MrGodSquad:
unless I’m misunderstanding what you’ve done, from what I can see you’ve done nothing wrong. so you drove the truck back to your yard with your card in slot 2? there is no problem with that
Is this meant to be a joke 
Anyway OP, the best thing to do in that situation would be to do a vehicle printout and write the explanation on it and show your start time and the time you took over the vehicle, that way you’ve got an accurate record of your activities on the printout, don’t forget to sign the printout.
I generally think its best to do 2 printouts, hand one in when your card is downloaded and keep one with you in case you get stopped, you’ve got to keep one with you for 28 days anyway.
I’m assuming the printout you did was a card printout, if you have access to the same vehicle you can still do a vehicle printout for the day/night in question or get the usual driver to do them for you, if you was driving the vehicle before and after midnight you may have to do 24 hour printouts for both days to get all your activities.
If you get stopped and show the DVSA bods your vehicle printout/printouts they will be able to see that it was a genuine mistake.
Learn from it and move on 