pluging tire question

[scott2007nomad]

I used the Stop and Go to mushroom plug my rear tire 2 months ago. Has not last any air since then.
The plug didn't "set" at first since it had a slow leak (bubbles in the spit) but after I yanked on it a few more times with the pliers, it's been fine.

I would think since you had a hard time getting the rasp in, you puncture is small, so it must be something on the inside preventing the plug from setting.