"The system however gave the trip to the junior pilot to facilitate a separate trade with the senior pilot. "
If what you are saying is true then the program logic ran the Jr. Pilot's trade out of seniority in order to accommodate the Senior pilot's trade.
That's still wrong. The logic should be (but wasn't) the Senior pilot's trade couldn't be accomplished because it wasn't available. Then the writer of this thread should have gotten his/her trade in the proper order.
Now if there was a pilot to pilot trade here that should be OK.
It sounds like a senior pilot built the trading logic.
If this is true, being a senior pilot I could look through the trade requests of those Jr. to me and pick a trip I wanted to fly that someone else wanted to trade into another open trip. That's called "cherry picking" the system and in reality is "super" seniority.
In the past senior pilots got seniority trade in the "big pick" (1st trip trading after line completion).
Maybe we can fix this with all the reserve gripes?