This is merely a curiosity question. Is there any reference to Pesach Sheini mentioned in the Haggadah either directly or by metaphor or "hint", perhaps in one of the "songs", esp. after Nirtzah?
The most obvious reference to Pesach Sheini is by Korech (my translation):
זכר למקדש כהלל. כן עשה הלל בזמן שבית המקדש היה קיים, היה כורך מצה ומרור ואוכל ביחד, לקיים מה שנאמר על מצות ומרורים יאכלוהו.
A remembrance for the Mikdash, like Hillel. Thus did Hillel do when the Beis HaMikdash stood, that he would wrap Matzah and Maror and eat them together, to fulfill that which is written, "On Matzos and Maror he should eat it."
Tallelei Oros Haggadah (page 363) quotes the Belzer Rebbe, who asks: Why do we quote this passuk, dealing with Pesach Sheini (Bamidbar 9:11), and not the similar passuk by Pesach Rishon, ומצות על מרורים יאכלוהו (Shemos 12:8)? He answers that לקיים מה שנאמר doesn't mean that he fulfilled that, but rather it's a tefillah that we should be able to fulfill this passuk. We can't quote the passuk by Pesach Rishon, because it is Pesach Rishon; instead, we quote the passuk by Pesach Sheini as a tefilla that we should be able to fulfill it this year. (It then goes on a tangent about if Pesach Sheini applies to a community that's beyond the scope of this answer.)