I'm assuming that I can't find an answer to this question because it is a bad idea. But I have sneaky little dogs that prefer to pee inside during bad weather. I truly don't care one bit about the warranty. This is a small area in a teenager's bedroom, not the grand entrance to the White House.
1) Is polyurethane a must-not-do?
2) What about other hardwood finishes?
3) Oil?
4) Okay, what about waxing it?
5) Come on! Someone help me!

You could do a screen and recoat, that may seal up the joints. If it is a beveled edge then you need to find someone that has the new flooring abraider, it gets into the grooves.

It can also be sealed at time of installation but thats another story.