I didn't have any specific source in mind when I made that comment, it's just something I've seen in general. To double-check, I did a Google search for "most reliable used cars", then clicked on the first five links that didn't involve a price ceiling. Four out of five listed the Prius as being among the most reliable. For reference, here are the links I found:

https://autos.yahoo.com/blogs/motoramic/car-dealer-scientifi...

http://www.forbes.com/pictures/ehmk45iidj/toyota-prius-2/

http://editorial.autos.msn.com/18-most-dependable-cars-on-th...

http://www.edmunds.com/car-reviews/best-used-cars-2013.html

http://wallstcheatsheet.com/automobiles/10-most-dependable-c... (This is the one without a Prius, but even this one has a hybrid on the list in the form of the Volt.)

Anecdotally, I seem to see a disproportionate number of the original Prius on the road still, despite only selling 54,000 of them in the US, and being over a decade old at this point. That could, of course, just be confirmation bias or local demographics.