I thought my yeast was dead…maybe not?

So i got a smack-pack of wyeast forbidden fruit in the mail and its manufacture date was back in july.
I said the heck with it, and made a starter anyways.
No activity in the starter to speak of. I was unhappy to say the least.
I made the starter on Saturday and left it, ignored it. I didn’t even want to think about it
I passed through the room it was in today (monday) and saw a single bubble in the airlock.
I swirled it and the airlock went crazy, as I’m used to starters doing
Is this maybe just a long lag time because the pack was so old?
Should i pitch this yeast? should i make a new starter from the yeast?
I cant get another smack pack without paying shipping again, and i really dont want to do that, i could get a dry belgian yeast to pitch but i really like forbidden fruit
any help would be appreciated.

How big is this starter (qt or litters)?

How big is the beer (OG/gallons)?

2 qt starter
The beer will be in the ballpark of 1.065

According to the MrMalty and YeastCalc, you only started with ~1% of the yeast being alive. But I’ve read that those numbers are really conservative and there are a lot more yeast alive.

I would do at least 1 more starter. Closer to 1 gallon if you can. If you can’t, ferment it cool and time it so you can pitch the whole thing in the beer at high krausen?

I’ve made starters with old smack packs, but I’ve stepped them up, starting with a pint. (And that was packs I kept in my fridge for months, I would complain to the seller if I got a smack pack that old.) I think you’ll get there eventually, but I agree with nighthawk, I’d step it up.