I have a suggestion:
Step one: Do everything you can in the time you have.
Step two: Front up and say, "My login device arrived late, but I have finished this much, and if you give me _realistic estimate of time required_ I will have the rest done"
I figure direct honesty shouldn't make things
worse, an' there's a chance you'll get
some slack if you don't make up excuses (I would've got it done, but the thingy arrived late and...), show some effort (by doing most of the work), and state simply what you need to complete the task. Might help to go to him rather than waiting for him to find you (to avoid giving the impression that you're trying to avoid the issue), but it depends on the individual.
Whether this helps or not, I hope things work out okay for you

.