I thought about that, too, Carsten. But I think restoring the entire session (including the previously scanned items) after clearing it would be a non-trivial amount of additional effort.
Also, I think you probably already know this, but just in case: items are checked out as they are scanned. So, when the session is cleared, it doesn’t mean that the scanned items aren’t checked out (they are).
So, I think for the first iteration of this feature, it should be sufficient to allow easy restart of a new checkout session with the previously scanned patron. This would allow you to continue checking out new items to that borrower. If you wanted to see the items you previously checked out, you could always click through to their Loans page (there’s a quick link to that page from the Checkout page).