Were Children of Israel killed in the plague of the firstborn?

Question

We know from Torah that all B'nai Israel who:

• Ate the Passover lamb
• Did not eat leavening (bread and beer)
• Were inside at midnight (and stayed inside until morning)
• Were in a house whose doorposts were properly marked

were spared from the plague of the firstborn.

Their animals were also spared (it is not clear how, though the flocks would be too numerous to bring inside):

But to all the children of Israel, not one dog will whet its tongue against either man or beast, in order that you shall know that the Lord will separate between the Egyptians and between Israel. Exodus 11:7

We also know that non-Jews who did the above things and chose to take on the rules of Judaism (and were circumcised if male) were spared. Exodus 12:48-49

But what about Jews who were in Egypt but not able to go to a house and partake of the Passover meal?

Although the Hebrews lived in more of a serf-like state (keeping their own houses and communities and choosing their own family units), they were slaves in the sense that their lives did not belong to them. Pharaoh worked them any way he chose.

It follows that there would be Hebrews who worked in the palace, in the turquoise and copper mines of Serabit el-Khadim and Wadi Maghara (real mines of the era with archeological evidence), and possibly some others elsewhere.

What have commentators said about this, if anything? Or what can we assume? I can think of several possibilities:

• There were no Jews in the entire land of Egypt that were too far or not able to return to the Jewish community and eat the Passover meal with their family or someone else. This seems quite unlikely to me, but I haven't found evidence to the contrary. Edit: there are commentaries that speak of Jews being taken to tutor Egyptian children and perform other tasks away from their places of dwelling.
• These Jews were subject to the plague and many died.
• Moses was able to send messages and advise them of what to do ahead of time (there at least 2 weeks between the 9th and 10th plagues).
• Angels or other messengers of God told them what to do (or they had dreams or they "just knew").
• They were spared without following all or any of the rules.

Answer 1

Rashi Shemos 12,13 mentions like the questioner that their were some Jews stuck inside Egyptian houses (maybe for the very reasons the questioner mentioned) and they weren't able to put blood on the doorposts. But Hashem still saved them (same probably apllies to the Jewish owned animals which could not possibly fit in the dwellings) because they were Oneis (Unable to fulfill the comandment):

"ולא יהיה בכם נגף" - אבל הווה הוא במצרים (מכילתא) הרי שהי' מצרי בביתו של ישראל יכול ימלט ת"ל ולא יהיה בכם נגף אבל הווה במצרי שבבתיכם הרי שהיה ישראל בביתו של מצרי שומע אני ילקה כמותו ת"ל ולא יהיה בכם נגף

Rashi is quoting the the Mechilta D'rabbi Yishmael

רבי יונתן אומר ופסחתי עליכם, עליכם אני חס ואין אני חס על המצרים. הרי שהיה מצרי בתוך ביתו של ישראל, שומע אני ינצל תלמוד לומר ופסחתי עליכם- עליכם אני חס ולא על המצרים. הרי שהיה ישראל בבית המצרים שומע אני ילקה בגללו, תלמוד לומר ולא יהיה בכם נגף בכם אינו הווה, אבל הווה על המצרים
Rav Yonasan said The word "Pasachti" means to have pity, on you (Israel) I (Hashem) will have pity but not on them (Mitzrayim).... So if an Israelite was in the house of an Egyptian he (the Israelite) might get plagued because of his proximity, The Torah therefore teaches "THe plague will not be on you" it won't affect you rather only the Mitzriyim.

Answer 2

The verse (Exodus 12:22) states:

ואתם לא תצאו איש מפתח ביתו עד בקר

and you shall not go out, any man from the entrance of his house until morning

The Talmud (Bava Kama 60a) says on this verse:

כיון שנתנה רשות למשחית לחבל אינו מבדיל בין צדיק לרשע

Once permission has been given to the Destroyer to damage, he does not differentiate between the righteous and the wicked.

It would seem clear from this that any Jews who failed to be inside a house during this time was killed. As far as your concern that they were still slaves, the Talmud (Rosh Hashanah 11a) states that on Rosh Hashanah the slavery ended, and in Nissan (six months later, Rashi (ibid.)) they were redeemed. So at the time of the tenth plague they were no longer slaves, and were able to freely move about Egypt.