Milk stains still visible from the outside?

So, about a month ago, I spilled milk on my 11" i5 and had to pay the standard tier 4 $800 or so to get the full repair done to the insides and stuff. At the time, I had spilled milk that entered through the back vent grills and so when I got it back, I assumed they had taken care of the stains and such. But a week or so ago, I was blowing some dust out of the open ports and such when I looked at the grill area and discovered dried stains (i THINK) that looked suspiciously like the initial dried milk stains that were still visible from the outside. I was in disbelief because I thought they would have cleaned such stains, and especially since they promised that I would retain my warranty after this hefty repair, I became concerned since if I ever take my mba in for a service repair and they open it up to see the stains still there from my first repair, wouldn't they try to accuse of having spilled milk in there and void my warranty again?

I'm not really sure what I should do, since I don't exactly have easy access to the nearby apple store. If I did, I'd tell them to take a look inside and see if the stains are still inside or something.

sorry if that initial post was too long and convoluted, I guess a better way to phrase my question is:

Does apple clean the insides of the computer if there was liquid damage that wasn't water?