If you accidentally sent coins to a BTC address they will not show up on the BTC network. BCH supports the same address format as BTC. Funds would get sent to the same address but on the BCH network instead.
Recovering coins sent to a BTC address depends on where the BTC address came from. If the BTC address came from a program that gives you access to your private key, you should be able to load that private key into a BCH wallet (see related questions).
BTC addresses can come from many different sources. If the BTC address came from a service that does not give access to the private key then you will have to find out if that service supports access to funds sent on other networks.
Once coins are sent they cannot be cancelled. Since Memo is the sender and not the receiver, there is nothing that can be done on Memo's end once funds are sent. Access to the coins is entirely dependent on the service or application where the BTC address came from.
The Memo application shows balances and profiles for all addresses that have been used on the BCH network. Seeing the balance or profile with the corresponding BTC address does not mean Memo can access the funds.