If this was a bodily fluid and the "friend" identified it as such, I am certain that property disposed of the item. Cleaning it with anything else is out of the question.

Seems to be quite reasonable to impose a charge. Not sure who else would be responsible. C

Whether the specific amount is reasonable is up for debate. If the friend believes it to be excessive, he should raise that with a manager while he is still at the property.

But, as others note, this whole thing seems to be a game of telephone. Missing lots of detail which may be important.