I had a very similar situation about a month ago, I staked my QTUM through Qtum Core Desktop wallet. And one day I thought a couple of hundred coins disappeared, but it turned out that when mined coins getting in a stage to be matured it will be in a locked position. So after a day or two, all the staked portion of coins plus mined coins showed up in my wallet. I am hoping that is what it is in your case as well.
Posts made by Nanook
RE: missing qtum from core wallet?