Hi comspec Welcome to the forum.
My daughter had the same issue but luckily got the phone working after disassembly and drying. I asked her to dry for a couple more days to be sure.
It sounds like you did everything a sensible person would do, so it’s a bit upsetting it didn’t work.
Can you get the battery checked for voltage? You would want it to be above 3.8V and maybe you could get it charged.
There are fairphoneangels and maybe one is near you that could lend you a battery.
The drying really works better in a flow of air rather than static, as just on a towel. I would try a bit more drying. Did you notice a red square?