I was looking for a solution as well when I found this post from 2015. Its Oct 2019, has anything been done on this? Now that reviews and CRMs are tied to email, it is REALLY a pain when email is not attached to an order. I have several POS orders that need email added. It's not always easy to get it while checking someone out. Please advise.
Just ran across this old, long thread and would echo the sentiments. While you can tag a customer's e-mail and shipping address after the fact in the web admin, this doesn't actually link the real Shopify customer record with the order. Which is a big deal. For integration purposes we need to link these. Either that or if there was an option to require a customer to be identified for each POS transaction where the operator doesn't shoot themselves and us in the foot.
Agreed with Greg. Maybe in Canada they aren't concerned about getting the contact information for a customer that decides to pay with a personal check, because everybody has money and no checks bounce. But in the US, personal checks sometimes are not good and a customer account/name/info really needs to be attached to that POS order. The clerk ringing up the order is not happy when he/she forgets to do that, and the check bounces and the clerk ends up having to pay for that order.