It's actually scary how often this happens.
A lot of quick lubes have a very self-derogatory view of their work. "It's just an oil change, any idiot can do this." Yes, any idiot can remove a plug, put a plug in, and fill a fluid. Idiots cannot be trusted to remove the right plug, put the plug back in without damaging it, and fill the correct fluid to the correct level though. A lot of idiots cannot differentiate between a transmission or an engine, and you are lucky if they happen to notice the color of the fluid is wrong.
I worked at a quick lube and at a shop that apparently had aspirations of being a quick lube. Saw it happen at both places. Heard stories about other stores in the chains.
I personally saw one where an idiot drained the trans on a 4Runner (HOW CAN YOU NOT TELL?), then the guy up top added to the engine and started it. The guy up top pulls the dipstick, and it is several inches past the full mark. I go downstairs and ask to see which plug was removed...guy points right to the trans..."that's the engine, right?"...me: "oh [censored]." Engine was drained, trans was refilled with incorrect fluid (Dex/Merc), customer was never notified of what happened, per the upstanding management.
Another time with a Saturn I hear a different guy down below say "why dis [censored] comin' out red?" Again, I go downstairs to look, again, "oh [censored]." He took the filter off with the claw pliers too. Dented and scraped it all to [censored]. Again, per the upstanding management, the filter was screwed back on and checked for leaks, transmission was topped off.
At a different store across town, I heard a story about someone draining the trans and overfilling the engine on a Subaru, and the car left out of the shop that way. It didn't make it far. $7K in damage or something like that.
I'm never going to work at a place like this again if I can avoid it. Their attitude towards what they do is very poor. The "any idiot can do this" attitude gets them into these situations.
I am not saying every place that primarily does oil changes is like this. Some hire good people and do a good job, but from the customer's perspective it can be hard to tell. It only takes one idiot and one manager who likes to sweep things under the rug to tear your car up.