I would expect they would have lost some potency, perhaps a lot, perhaps a little. But in the future, really, just get a glass jar. They're not hard to get or anything and a plastic bag is far from airtight. And get a packet of dessicant/silica gel to put in with them to absorb any moisture that does ghet in. And keeping them in the fridge or freezer, so long as you have a dessicant packet, is the best way to go. Bascially you need to keep them away from heat, light, moisture, and oxygen as much as possible.