If you accidentally sent BTC to your memo address it will not show up on Memo. BTC supports the same address format as BCH. Funds would get sent to the same address but on the BTC network instead.
Memo does not support accessing BTC funds. If you sent BTC to your Memo address you would need to export your private key and import it into an application that supports BTC.
WARNING: Importing your private key into another application is dangerous and can lead to loss of funds. Only do this if you are an expert and understand the consequences. Memo does not offer any support or take any liability in trying to access funds sent on other networks.