What exactly did Picard do with Stargazer that was so "outstanding"? If Picard really did command (and not just serve on) Stargazer for 22 years, it was probably a mostly humdrum and uneventful service.
It's not clear how Picard distinguished himself as her captain. What's known is that Picard gained command of the vessel at a young age due to the previous captain's death. Picard's biography states that he was born in 2305. The incident in which he took command of the Stargazer's
bridge happened in 2333. The Stargazer
was lost in 2355.
Picard may not have been promoted directly to captain after the incident, but may have instead been promoted to full commander before earning the rank of captain at a later date. He could still have captained the vessel, however, as one need not hold the rank of captain to serve as a ship's master. This being the case, several years may have passed before he actually earned the rank of captain, in which case Starfleet would not have promoted him immediately after his assignment on the Stargazer
was over: that he lost the ship makes a promotion even less likely.
Nine years is a long time to go without a command. An officer with the rank of captain may serve in other capacities, however. Perhaps Picard had other assignments that drew his interest before the Enterprise