Could this have been what damaged my camera?

My camera wasn't focusing properly, and sometimes did not want to focus at all (nikon d3100), however it has now been repaired.

I'm wanting to know if this could have damaged my camera:
I was using it with a lens that can be switched to M or M/A, and when switched to M/A, you have to half press the shutter, let it focus then you can manually adjust the focus if you want to. If I manually adjusted the focus while the camera was still trying to automatically focus, could I have damaged it?

That could have damaged the lens but not the camera's AF system

What was repaired on your camera?

I don't see how that would damage the camera though. What you are describing sounds like it would be a lens issue. I know that there are different types of focus motors and they all handle auto focusing different.

Some of the cheaper ones can strip a gear if you attempt to manually adjust the focus when it is in A/F. With others, you need to wait until it has focused, then fine tune it. There are some that do allow a manual over-ride but that is normally the top of the line lenses.

No, that won't harm the camera or the lens…
M/A is a manual override on certain Nikkor lenses, The idea is that you can take over from the autofocus at any time! It can be useful in low light/low contrast imaging, where the AF hunts for focus.

M = Manual Only

A = Autofocus Only

M/A = Manual Override - Usually on a newer SWA equipped lens

[EDIT]
Directed to the idiot who gave the thumbs down and not the original poster (there's always one):

AF-S NIKKOR lenses feature Nikon's exclusive M/A mode, that allows switching from autofocus to manual operation with virtually no time lag - even during AF servo operation and regardless of AF mode in use.

Taken straight from Nikon's site here: http://imaging.nikon.com/...ossary.htm

So Stick that in your pipe and smoke it!