Should I add more yeast?

Brewed a 1 gallon batch yesterday.  I had a no. 6 rubber stopper in the top with a 1/2 tube for blow-off.  Just checked on it and and found that the stopper was blown out of the top with a few clumps of yeast dried on the side of the bottle.  Not sure when this happened.  My question is, should I add more yeast since it looks like I lost some, or should I wait to see what kind activity I get over the next day or so?  Hopefully I can salvage this batch.  Any ideas?

I just had a similar issue with a starter on my last batch and it turned out just fine.  There was enough yeast left in the wort to get me pretty close to estimated FG and it tastes great.

Thanks jtoots for the reply. Hopefully mine turns out like yours and won't be poured down the drain.