Think about it logically man if a cop got called and the person calling said they smelled a little bit of weed do you really think they're going to go out of their way to respond? Maybe you live in a town with little crime and the cops have nothing better to do but if they did respond they'd still have a difficult time...

I've driven down the road before and gotten a hint of weed in the air but I have no idea where it's coming from, so unless someone sees you it's pretty hard to pinpoint where exactly it's coming from. As long as you go inside directly after the cops would have to either get a warrant for search (something that isn't worth it for a tiny bit of weed) or get permission to come in which it sounds like your parents wouldn't give.

So as long as your quick about it, don't get spotted, and cover your tracks I don't think you have anything to worry about. Store your piece and stash in a smell free container (Mason jars are the best), do it at night where you're out of sight, and stop worrying because unless a cop is driving down the road at the exact moment your smoking there's little chance of them hunting you down.