What is the "everything" that you took out of the tank and rinsed with plain water? I would read up on velvet and fallow periods.
I would not, personally, reuse any item from a tank that had had velvet unless I had bleached the item or, preferably, let it sit for the fallow period needed to get rid of velvet. I say this because I had live rock shipped to me earlier this year. The rock was in transit for 4 days, with some damp paper towels around it. Many many critters survived that four day period not submerged in water, including stuff (like sponges) that isn't "supposed" to survive if its exposed to air at all. I think partly critters are tougher than we think and partly that its very possible for there to be small pockets of saltwater within rock that are not very easy to rinse out.
I think its incredibly likely that even if you rinsed your rock you could have velvet surviving somewhere in it, unless, as I say, you bleach it thoroughly or let it sit for the fallow period.