Man be careful sending directly from Square Cash. It is traceable. I use Cash App; but I transfer it to my Binance wallet, and from there to Electrum, and from there to Exodus, etc. etc. before transferring to the seller's address.
But for your problem, I cannot imagine them needing your sending wallet info. I'm sure you have a confirmation that xxx number of Bitcoin went to their receiving wallet (which should still show an address). That should more than satisfy questions their questions about payment being sent.