Id be fairly confident that they would. They also are encoded so that receivers that literally have no idea where they are can train on the received stream. Also don't forget that the receiver needs to hear signal from at least 3 or 4 satellites to be able to triangulate their position and altitude.
The wikipedia page has some info, looks like various CRC and parity checks. Maybe the receiver was just ignoring them, and receiving faulty data.
I dunno, it seems to me like that GPS receiver had fairly bad software. If you get packets from a bunch of different satellites but one is way off, it seems like good sense to throw that one away.
