The Knuth prize is different from the reward given for finding a bug in TeX.

Knuth's checks have their own wikipedia page: https://en.wikipedia.org/wiki/Knuth_reward_check

From the Wiki page:

> Very few of these checks were actually cashed, even the largest ones. More often they have been framed and kept as "bragging rights".[4][5]

Cashing a check only removes it from your possession if you hand it in to do so. Banks these days need only a physical scan of a check, e.g. via mobile phone deposit. Why not do both? There's nothing wrong with taking payment for your efforts.

AFAIK, after deposit, you're supposed to void a check by either destroying it or writing something on the front of it (such as "void")

(void*)