I recently bought a couple of baggies of assorted pieces at a quilt show - they were in the sponsoring guild's members sale. I always wash and dry my fabrics. I wash new pieces with the towels or even with regular loads, and alway put color catchers in for insurance. Then I'll add them to my stach. This way anything in the cabinet is ready to go.
Since I was unsure as some didn't feel like they had been washed, I washed all of them so I could use with confidence whenever I would want to use them with other fabrics from my stash.
The pieces that were already cut into patches I put in a lingerie mesh bag to keep them from going down the drain(just in case) and to keep them somewhat corraled. This seemed to work out ok for me.
For a Pattern suggestion for your find I just saw a darling pattern in Quilt Magazine -the October November issue pgs.90 & 91 have the picture. It is all half square triangles. I checked the cover and since it is displayed until Oct 11 I bought it as I want to make it and didn't want to risk not getting it. I will try to scan and send a picture tomorrow if you like.