The example given is from one card, so I consider that one instance. One instance = one example. I've never read another example than that one that I can recall. ST used it in his book and in interviews--but only that one.
We've seen several examples of PR's actual notes to different people but none of them contained initials used for an "acronym".
Do you recall that Thomas thought SBTC was an acrostic rather than a acronym?
from ABCNews online chat:
Steve Thomas at 12:08pm ET
You know, we searched high and low, far and wide, and heard everything from "Saved By The Cross" to Ramsey's own suggestion of "Star Base Technical Command," but were never definitively able to attach a source to that acronym. However, an open Bible on Ramsey's desk in the house, NIV version, Psalms 35-36, verses 1-4, contains the acrostic SBTC, backwards.