Hate to burst your bubble but accidents happen. communicate with the owner and see what Google with also tell you about pulling blood stains out of items.

Hand wash the stuff with cold water und regular soap. Let it soak for while, if its already dried out. Accidents happen, don't worry too much.

Ah, this is easy. Murder a hobo and drag his body into the cottage. Tell your host he broke in and you fought him to the death. Your "very tidy person" reputation is at stake!

hydrogen peroxide and scrub, it'll do wonders

Definitely not a YDI since accidents happen, but offer to cover the cost of cleaning (or replacement if they can't be cleaned to like-new condition) for anything damaged. That will likely go a long way to soothe any ire and is the right thing to do.

cold water only. hot will mess it up and set the strain.

That doesn't make you untidy, just clumsy. You can always replace the towels and rug and they'd probably never notice. :D