The OP unfortunately has no experience in building but has at least the eye to spot studs that 99.7% of the population would be suspicious of. Not to be rude, but they must have seen you coming(it was the lowest bid wasn't it?). I can't imagine any builder trying to pass that stuff off. Now, if Mexicans are on the job that's another wrinkle. They are about as smart as rocks sometimes. I was having a tile floor installed in the kitchen. When the helper went to the store for more tile the Lot/Run No. was different. Didn't matter to him, he just kept on putting them down. All that had to be jacked out(more dust all over the house) and replaced.
If I should die before I wake...great,a little more sleep.