That's BS man... unless there was oil pouring down the side of the filter or they flat out forgot to put it on I VERY seriously doubt they did jack wrong (this time anyway).
You already had a knock, just because it disappeared (VERY briefly) before this happened doesn't rule out mechanical failure due to wear or the fact that (as you admit) you were running her WAY low on oil...
Suck it up man... it's quite likely you're the one at fault here.
__________________
If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum.
If you're so inclined I'm always more than happy to accept tips via PayPal. 
Tip Jar ---> 
|