Took my new (but previously owned) Sig P238 out for the first time today. It shot wonderfully and I couldn't be happier, however, I lost a damn grip screw!

Previous owner said he only put about 200 rounds through it and it popped out sometime during the second mag so this is unacceptable in my opinion. Fifteen minutes of sifting through casings on the ground turned up nothing. Think Sig warranty will cover it? If not, any ideas where to get grip screws online? I can't find anything with google. Maybe the screw is the same size as other Sig grip screws?