I don't see any text that says you lose it. In this case, if it were at my table, I'd say the player can keep the Feat (it's still active/counts/can be used).
However, this could potentially lead to some problems, or at least some weird situations. For instance, if your stats were temporarily increased, and you were able to take a Feat (Hefty Hauler, on page 167, pre-req 12 Str), and then your Wizard went down to his normal 10, but could keep the Feat, that would be odd.
We could probably benefit from an official ruling on this, and maybe a new rule should be written, or the Feats in general should be proof-read again.