First of all, it's the OTC. Shares could have traded below the bid or above the ask. It happens all the time. It's happened many times to me.
But trading in between the bid and ask? That's not special at all. That happens even on the exchanges.
Even on the exchanges, bids and offers do not have to be shown if they don't meet minimum size requirements (250 shares doesn't), but the OTC has NO requirement for MMs to show bids or asks. Also, if there's a restriction (minimum quantity, AON), many MMs won't show the bid/ask.