Guild Wars 2

I missed unlocking a mastery I had activated for training once it was ready and kept doing events/kills for some time.
Where does my XP go until I activate another mastery for training?

Edit: Clarification

I don’t know but I feel like it just goes into the next mastery with the lowest progression because I have mastery XP in masteries I never selected

Well bummer… I wish it would go into masteries that are almost topped anyway.
At least it doesn’t just ‘disappear’.