Newer Member Intro and Question

Hello All,
I'm overdue to introduce myself as a relatively new Prius owner. I actually picked up my 2011 Prius 2 in early January 2018, and have been driving it hard each day since. I have had a 2016 RAV4 Hybrid for 2 years, and now my wife drives that vehicle.

I bought my 2011 Prius with 71,000 miles from a private party. As I use my Prius for a delivery vehicle, it is on the road 7 days a week. Over the last 3 months, I've put 10,000 miles on it. I transferred the 7 year, 100k warranty from the previous owner, so I've got basically 8 months and 19k miles before my warranty runs out. Reading much of Prius maintenance advice here, I changed out the 12 volt battery (with the OEM Toyota battery) and plan to do fluids this week (trans, both coolants, and brake fluid, as well as lube the brake slide pins, etc.

I read up on the inverter concerns, and had one unusual occurrence that perhaps another member can help explain a possible cause. Back in January, I was driving at night and all of a sudden, both dome lights came on, dashboard triangle lit up along with chime sound, and a message displayed as "key detected in vehicle". All of this chaos lasted about 10 seconds, and then it disappeared. It would be good to know if that is something I should be concerned with, as I will take the vehicle in this week, and want to document it prior to end of the extended warranty. Any help or advice here is appreciated. Thanks all!