03 civic no electrical power

This is for a coworker so my info is limited on the car. The car had no electrical power at all, no dome lights, nothing (engine cold after sitting overnight.) Attempts to jump the car would not give any power to the systems. After sitting for a while, the car started normally without a jump with all systems functioning. The battery is fairly new and had a good charge and the posts were clean (cleaned again anyway) but had no effect. Nothing else was done except the car sat for half a day. Any ideas?

There is an issue with the main fuse for those cars. I forget what issues they have but I remember replacing a few a while back. I'll look up the TSB tomorrow.