A lot of frustrating little things happen. A small strategy to mitigate that aggravation is to remind yourself that -- no kidding -- "Frustrating little things are part of the process."
Seriously, they're part of any new process, whether you're following an established path or pioneering. Documents get lost or deleted, email you thought was sent will be sitting in your drafts folder, you'll get a parking ticket mailed to you after you already sold the car and transferred the registration.
You've more-or-less got to deal with that sort of nonsense (even if "dealing with it" is just mentally accepting the consequences and moving on). But you can either get aggravated about it -- not smart! -- or remind yourself that it tends to happen.