Why can't I find some customer accounts in search on Shopify?

Also having the same issue. Extremely frustrating and we’ve only been open for 4 weeks. I had this happen to me 3 times today, no way to look up their email in the system, but i specifically remember entering it and the rest of the data is in their customer profile. When i add the email, it says its taken, but i cant search the email to find where it is “taken” because it isn’t actually taken by any other account, its just gone. This is unacceptable for a POS system - its the basics.