Why did my (car brake) floating caliper come loose?

So my front passenger wheel started making a clunk sound that got worse over time. I was finally able to jack it up and check underneath. While checking the bearing I noticed the floating part of the caliper was askew and now laying against the wheel somewhat held on by the pads. I can’t take the wheel off since the shop I took it into did not return the lugnut key (like an idiot I didn’t check) so I need to get a new key* and take the wheel off.
I do my own brakes (the last time was the only time I haven’t for reasons. That’ll show me) so not knowing why it came off and assuming it may need a brake job anyways because of uneven wear on the pads, should I just bite the bullet and take it in to a brake shop?

I’ve made up my mind to replace all of the lugnuts in question with ordinary ones.

My first thought is that your floating calipers aren’t floating. If the pins are stuck, this can cause the bolts to come loose and will also cause uneven wear on the pads.

Did a bolt back out? If so it’s a virtual certainty that it wasn’t tightened properly. I’ve never seen a seized caliper slide or guide pin cause a bolt to loosen.

Why would stuck float pins cause caliper bolts to come loose and back out?

The way it was explained to me, a stuck pin causes the caliper / pads to twist slightly, creating an uneven force that causes the bolts to loosen.

That’s the theory, anyway, according to someone who otherwise seemed to have some decent mechanical knowledge.

Based upon your description, you have either missing or broken pin(s) most likely caused by improper (over/under) tightening of the retainer nuts.
If the caliper is touching the wheel, you have something catastrophic going on with your brakes…I suggest you carefully limp the vehicle to a pro.

Caliper bolts (pins) were gone. Guess they got loose and fell out after a couple months. The one time I have a shop do my brakes …

I think you know the cause, the rest is just details.
I use a shop that can do brakes right, but one time they were backed up for two weeks and I was impatient and went somewhere else.., you can guess the rest.