I have a large black plastic tote in the trunk of my car. Every piece of fabric, whether it be cut length, clothing, or anything else - regardless of where I get it from, goes into a heavy black mil bag then into the tote. It remains there for 4-5 hot days. Thrift shops are not the only place these bugs can catch a ride from. Believe me, you DO NOT want them in your home, so deal with your fabric (or any kind of material) before you bring it indoors.
Just a few days ago bed bugs were found in a police station in the Philadelphia area!