I heard a shiur where this Gemara was quoted, but forget the exact source. Anyone know where this can be found, or if i misheard? TIA
Especially in light of the parsha timing, I'd guess the comment above (thank you R' Interested!) hit it on the head -- a Medrash on Avos that comments when the Torah says "the Torah is not across the sea", it means "those who spend all their time sailing the high seas to make a living aren't going to learn a lot of Torah."
אין התורה מצויה בתגרים ובסוחרים יורדי הים באניות
A major, major caveat is that a very great rabbi -- and businessman -- addressed this. Rabbi Avraham Danzig, author of Chayei Adam and Chochmas Adam, writes in his introduction to the latter that his family's tradition was to be self-supported (a grandfather of his "fed ten children in dignity, taught Torah to the community, and never took a dime from the community"). When R. Danzig published his works, people said you're that businessman running around the trade fairs of Leipzig and Frankfurt, what are you doing writing a sefer? Then they read his work and -- ooh, aah ... stopped complaining. He says that "seagoing merchants won't get the Torah" means if their entire focus becomes on making big bucks. Someone who continues with their priorities straight and heart in the right place can still do okay.
Without having been at the Shiur and hearing the quote directly, it would be hard to give an exact and straightforward answer, but here are two sources that may relate to what you're looking for:
Gemara Niddah 70b (emphasis mine):
שלשה דברי דרך ארץ מה יעשה אדם ויחכם אמר להן ירבה בישיבה וימעט בסחורה אמרו הרבה עשו כן ולא הועיל להם אלא יבקשו רחמים ממי שהחכמה שלו שנאמר (משלי ב, ו) כי ה' יתן חכמה מפיו דעת ותבונה
The sages of Alexandria also asked Rabbi Yehoshua three matters of behavior: What should a person do to become wise? Rabbi Yehoshua said to them: He should increase his time spent sitting in the study house and minimize his dealings in merchandise. The sages of Alexandria said to Rabbi Yehoshua: Many people have done so, and it did not help them to acquire wisdom. Rabbi Yehoshua responded: Rather, they should pray for mercy to receive wisdom from the One to Whom wisdom belongs, as it is stated: “For the Lord gives wisdom; out of His mouth comes knowledge and discernment” (Proverbs 2:6).
(While it doesn't explicitly say that this refers to Torah, just "wisdom" more generically, I have heard this source used in talks about the importance of Torah study)
Pirkei Avos 2:5 (emphasis mine):
הוּא הָיָה אוֹמֵר, אֵין בּוּר יְרֵא חֵטְא, וְלֹא עַם הָאָרֶץ חָסִיד, וְלֹא הַבַּיְשָׁן לָמֵד, וְלֹא הַקַּפְּדָן מְלַמֵּד, וְלֹא כָל הַמַּרְבֶּה בִסְחוֹרָה מַחְכִּים. וּבְמָקוֹם שֶׁאֵין אֲנָשִׁים, הִשְׁתַּדֵּל לִהְיוֹת אִישׁ:
He used to say: A brute is not sin-fearing, nor is an ignorant person pious; nor can a timid person learn, nor can an impatient person teach; nor will someone who engages too much in business become wise. In a place where there are no men, strive to be a man.
(Admittedly, this statement isn't as absolute as "won't acquire Torah", but it does imply that it's harder. Also it's a Mishnah, not a Gemara, but I figured that wouldn't automatically disqualify it.)
There are various Talmudic sources that allude to something of the sort, and they are collected by Rambam in Chapter Three of The Laws of Torah Study:
A person whose heart inspires him to fulfill this mitzvah in a fitting manner and to become crowned with the crown of Torah should not divert his attention to other matters. He should not set his intent on acquiring Torah together with wealth and honor simultaneously.
[Rather,] this is the path of Torah: Eat bread with salt, drink water in small measure, sleep on the ground, live a life of difficulty, and toil in Torah.
The task is not incumbent upon you to complete, nor are you free to desist from it. If you have acquired much Torah, you have acquired much reward, and that reward is commensurate with the difficulty [invested].
Perhaps, one will say: "[I will interrupt my studies] until after I gather money, and then I will return and study, [I will interrupt my studies] until after I buy what I need, and then, when I can divert my attention from my business, I will return and study." If you consider such thoughts, you will never merit the crown of Torah.
Rather, make your work secondary, and your Torah study a fixed matter. Do not say: "When I have free time, I will study," for perhaps you will never have free time.
It is written in the Torah [Deuteronomy 30:12, 13]: "It is not in the heavens....It is not across the sea...." [This implies:] "It is not in the heavens" - i.e., it is not found in the proud spirited. "It is not across the sea" - i.e., it is not found in those who travel across the sea.
Therefore, our Sages said: "Not everyone who is involved in business will become wise." Our Sages also commanded: "Minimize your business activities and occupy yourself with Torah."