1) Can a person detect if a bitcoin still has bitcoin cash in it?
2) Assuming 1 is yes, is a bitcoin with the cash still in it worth more trading than a bitcoin without?
Thanks!
Before answering your questions, I would like to clear one thing. It is not Bitcoin but Bitcoin address that matter. You have some wrong conception upon the idea of BTC/BCH. It will be more clear with following answers.
1) Yes. Suppose you have BTC on 1VodeDgeG4dh5noobtrsoRR23fkrR52sV (before 1st August), one can easily trace if this address still has equivalent BCH or BCH have been exported.
2) Nope. Both Bitcoin and Bitcoin Cash trade on different chains. Even if you trade BTC having equivalent BCH on same address, BCH will still remain on same address and only BTC will move. In short, both are independent and doesn't effect each other.
Tell me if you still have doubts.