Just a note there appears to be server issues on BMV site this morning, so links below might work or not.
Those plates pictured on the red car are permanent (metal) plates. The standard "In God We Trust" plate. You can see an example here, click the "Standard" tab:
https://www.in.gov/bmv/2620.htm
First couple rows at this link show images of what temporary paper plates look like, with "Temporary" clearly visible:
https://www.bing.com/images/search?q=indiana+temporary+registration+plate&FORM=HDRSC2
Indiana plates (registrations) are renewed by dates assigned alphabetically according to surname. You don't need to get a new metal plate every year, when you renew you get a new sticker that is placed on your existing metal plate. If there was nothing hinky going on with the car (valid registration, etc.) then their current registration sticker would've been due for renewal by 8/21. If not renewed, they would've been considered expired on 8/22.
https://www.in.gov/bmv/files/Registr...n_Schedule.pdf