You did a 2L starter in a growler? Isn't the size of a growler about 2L? Because there is your problem. If you've already done one starter, that yeast is active, healthy and ready to go. Plenty of people have had blowoffs used for starters.
I'd be concerned if too much was blowing off, because that is a lot of the nice healthy yeast you want to pitch. But as you said you should have plenty. An interesting note I picked up in Jamil's and White's Yeast book - if you kept using this yeast for a few generations, always in smaller containers with the top cropping yeast blowing off, you'd end up with the yeast that would naturally want to bottom crop / settle during fermentation. Not a bad thing, just an interesting note in the world of yeast.