I can almost guess that if their is a connection there it's probably easier to fix it than to rewire the post.

However, you can do what you want as long as the connection is made in some approved fashion and location (you just can't bury wire nuts no matter how much tape you wrap them with).

The light fixture is usually easily removed and you can look down inside the pole to try and see what is wrong.

I'm sorry, but this sounds like 'DEATH' waiting to happen.
WHAT, pray tell, is a 'ground electrical cord'?????
Did you mean to say that all but the 'ground wire'
of the cable going to your outdoor light was severed
by your digging?

What I meant by the ground electrical cord is the cord that goes out to the lamp post. I can't pull it out from the hole in the base of the lamp post or pull it out of the top of the lamp post after I remove the lamp at the top of the post. I thought maybe cut the wire leading into the base of the lamp post and run a wire down in from the lamp post top, connect the two and attach the lamp.

Any chance there's an "electric eye" in the post about 12" from the top? If so, maybe the loose connection is there.

If that doesn't help, then you can cut the cable off somewhere between the house and the pole and splice it to a new UF cable (that runs to the top of the pole) using a special UF underground splice kit. Beware, it's frequently a real challenge trying get a new cable to fit into an old post.

If it won't come out, then you haven't pulled hard enough.
(Dear Lord, give me patience).

Sounds like the numerous installations that embed the UF cable in the concrete at the bottom of the post.

There is no easy way to fix the problem since the old cable generally will not come out, and there is no simple way to get a new cable into the pole (dig a big hole, core drill through the concrete into the pole, spend more than a new pole on coring bits).