I just spoke with trip trade desk. I found out the following. I tried to pick up a trip in open time via STT. A junior pilot to me got it because he had something a senior pilot to me wanted via a trade. The senior pilot to me didn't and doesn't want the trip i want and has no request in for it. The system however gave the trip to the junior pilot to facilitate a separate trade with the senior pilot.
I could have understood if the senior pilot wanted the trip I wanted, got it, then traded it in a separate trade, seconds later. At least he/she owns it momentarily. But in my case, and most cases, the senior pilot never knew the trip in question was even open/available.