Why are you sure it’s not a battery issue?

I’m pretty sure that my Honeywell wireless thermostat displays “LO” when the batteries run out - they last 2-3 years though so I’ve only seen it a few times.

The longer you leave it the worse it will get. It might be cosmetic right now but might turn into a structural problem if you leave it for another 2 years. Find the leak, remove the rotten wood, treat the rest. If you need to economise you could put cheap vinyl down (maybe look for an offcut or damaged piece).