There was a second problem too... it didn't cache the templates that were being used.
And a third problem... the queries were inefficient... 3 seperate queries! 2 of those in a loop. So if you had the default 20 quotes set, then you would perform 41 queries in total. Really no need for that.
However, I shall give credit where it's due. The idea is brilliantly done and the database table is perfect

No crude and no playing with vBulletin tables.
Anyhow... could the hack author take a look at the version of whoquotedme.php I've attached and consider merging the changes into the one in your zip file.
I've added the template caching.
I've added the forum permissions logic.
I've reduced the whole thing down to 1 database query.
So on your average site it will only be 11 queries to generate the page and not 52.
The file is attached, I'm sure others might also want to look and merge the differences.