As Niagara1 mentioned, the moisture is either coming from a potential bad seal somewhere in the bag, letting in ambient moisture/humidity or the oatmeal still has some. Only way to know for sure is to seal them separately and see how it turns out. My guess is on the oatmeal, but again this is only a guess. Without going through a process of elimination it is hard to say from my PC
As to whether it will last 3 weeks or not in the wilderness depends on how much moisture has gotten into the fruit. Pliable is still OK and should last no problem, dehydrated fruit is pliable and has no issues in that state for long periods of time.
If it really worries you, just vacuum seal the fruit in single serving, then vacuum seal that little bag of fruit into the bigger vacuumed bag with Oatmeal and you have a fail safe. Little more work, but at least you will have peace of mind while you travel.