As a couple you guys will have many obstacles, fights and miscommunications. Everyone make mistakes. Relationships are all about having patience and forgiveness. Can't expect your partner to be perfect. He may sulk a bit but he should get over it pretty soon. If he can't get over a saved file then I don't see you guys working out at all in the long run.

It is your fault as you did not double check but it is hardly a big issue at all. He is old enough to get you did not do it intentionally.