How much to reattach a veneer that came loose?

If the veneer is truly in one piece it can be recemented. Most dentists charge a nominal fee to do this. You might consider returning to the original dentist who made the veneers. They will know the original processed for placement.

if veneers is oky, no damage, u can go for recementation, otherwise u have to go for new one. recementation cost varies, we charge US$40 for recementation.