Does anyone know if my coins that I transfered like 3 weeks ago from poloniex to my wallet are gone?
They are still not in my wallet and they don't awsner my support ticket for over 3 weeks.
Will they ever get back?

Is there any possible that Sia coins on Polo net just lost?

As per my analysis, Siacoin will be stable for weeks from now on, I think it will not receive more pump anymore any time soon. Either way, happy earnings!

I've also observed this. But this is more common with SIA. Initially, I thought the reason behind this was Polo, but after reading Reddit posts by SIA developers, I understood that it is due to their programming. Possibly, their integration fails when a large volume in place at Polo. Hopefully, it will be corrected so we can sell our coins to get profit.