Csfloat scam?

Hey guys I think I got scammed on Csfloat, let me explain.
Yesterday afternoon I bought a Vino Primo five seven, the seller in a hour sent me the trade offer but was not appearing in the trade section of csfloat, so for csfloat he accepted to trade with me but he didn’t sent any trade offer (from they’re pov). So I asked even to they’re support bot and told me to not accept the trade offer and wait until it appear on the trade section on the site.
This morning, while I was sleeping like any human, just before the expiring time, he updated csfloat and resulted that he sent me the trade offer but I didn’t accepted it on time. Is this a scam? I’ve tried to contact csfloat support but they talk with superiority and too lightly.
It’s just a shit transaction, was like 3 euro so the 4% penalty for me is some cents, but if this method work, scammers could earn lot of money from high value sells.
His trade offer is still available in my profile, I’m not gonna accept it, because he’s probably gonna reverse the trade.

Any suggestions is accepted.