I was in shop the other day and a young lady came in with her seatpost slumped all the way down in the seat tube. She had removed the seatpost, taking it inside of wherever she had gone (work?) and a thief stole the clamp and QR mechanism. Oy!

Anyhow, for the OP, it sounds like a non-QR solution is the best (cheapest!) answer to deter a quick thief.