You are right about the prospect part, I got mixed up with that. I'm not predicting the same success until age 41, but he did keep hitting upon return. The reason the Mariners never made the playoffs wasn't his fault, he performed up to his contract so far.
According to this Seattle editorial, I think the team keeps the money.
https://www.seattletimes.com/sports/mariners/maybe-teams-and-not-just-the-players-should-pay-up-during-suspensions-for-peds-use/