If you want to dry your swimsuit without your parents finding out then why don't you leave it to dry somewhere outside your home? It doesn't have to be wide out open in the public, but somewhere outdoors where the swimsuit can catch some sun and dry out. You can then collect it later.
I wouldn't worry too much about someone taking it, as generally people are not keen on reusing a stranger's swimsuit... But you may need to worry about people thinking it's trash and clearing it away or putting it in a trashcan.
That's why you should try and find somewhere fairly remote.
If you really think it's best to dry it indoors (or if it's too cold for it to dry outside where you are), then try leaving it in your room on a heater, underneath another piece of clothing like a coat or jacket.
Make out like you are drying that out (you could even splash some water on it) and keep your swimsuit below.
Also, all this sneaking about will get to you eventually. In the long run, you might want to consider talking to someone you trust, because there's really nothing wrong with whatever way you chose to live you life!
