Kids, whats going on?

I'm a new not so new guy here, first post. Ignore my ignorance and try not to laugh too hard at.

Know pretty much next to nothing about cars, trying to change that. Anyway I've got a honda accord 02, god it Dec 02, and something fell off it the other day.

From looking under I think it was over the section of the front axel where it connects to the drive shaft?

I've been driving a good bit with it off, I swung by a autoshop and it seemed like the guy was sizing me up for a ripping. The part doesn't seem too important or hard to install so i told the guy later. I probably should've went to the dealer I guess. People seem to think the dealer would've done the same. Isn't something like this covered by warranty? Its 4 years old and under 100k miles.