I would use it since it was obviously active & you know the yeast is good. If you weren't using a stir plate, a lot of that yeast probably dropped to the bottom of the growler anyway, so I'm guessing you didn't lose much yeast, if any.
One other note...I've read that you don't want to use a blowoff tube or airlock on starters because the yeast need oxygen to get going. Airlocks keep the oxygen out. I use a piece of sanitized foil over the opening of my flask/growler. Using a bigger flask also gives you more room so you won't end up with a mess. I just bought a second one because I found out my growlers weren't big enough on my last brew.
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