Trich may be able to be spread that way - it's debatable - but that means wearing someone else's clothes that are wet, like a wet bathing suit that hasn't been washed.
It doesn't mean your own wet pants. Like a cold or the flu or even COVID, you have to be exposed to a germ from someone else to get it. It doesn't just appear. Sexually transmitted infections are called this because they need sexual activity in order to transmit them.