Yeah, you're losing ALL power. I just pulled the negative cable off my batt. and put it back on....reset my clock and trip odometers. I'd voltmeter the battery, but I'm afraid it might be in you're ignition switch.
My truck was a stolen rebuilt, they offered to put in a new ignition assbly. but it was too high, so they did a pretty good job with the damaged one. If I pull out on the key when turning the truck over, it still starts, but I lose power to my radio & gauges momentarily. Hope that's not it in you're case though.