Normally the photographer kept the negatives, and stamped the back of the picture with his name, shop and such, I know the store I worked at had thousands of sets of negatives they they would go through every year and destroy anything over 5 years old that had not had any prints made off of them, that has been pretty much common procedure for several decades now, we purchased another shop a few years ago, that had a studio and in cleaning the place out, found thousands of negatives dating back to the early part of the last century. If it was a regular consumer lab and ot a pro shop, they normally would return negs as they do in the 1 hour labs now a days.
R.