This scene, along with a few others is included on a VHS tape that I purchased off of Neil back when it was still called Amateur Pies, I think. The scenes were not even advertised, they just happened to be thrown in at the end of one of his other scenes. It might have been this one (the happy homemaker), but I am not sure: https://piefightgirls.com/cgi/autogal.pl?vidnum=vdo-27-0094 Anyway, I am not sure if that scene and others made the "cut" when these videos were repurposed for downloads.
This was not a whole scene by the way. It was a bunch of small scenes that lasted a few seconds each. They were roughly edited. Sometimes you don't even see the girl get hit with the pie, just the aftermath. Anyway, I LOVE these types of old amateur scenes done by wammers. The video quality is poor but the attitude and enthusiasm is great. A lot of times it appears to be a boyfriend and a girlfriend or even just some girl the dude met in a dorm. Reminds me of the 1990s. WAMTEC has a bunch of these amateur-type scenes that I really like. A lot of dreck but some of it is my favorite WAM out there.
Number one: don't buy something due to my answer, the current owner of the site is really the only one who can speak with a guarantee BUT I made that site you see and over 20 years ago, the scene you are looking for was at the end of Volume 3
Like CKCP said, short scenes collected at the end of tapes.
Right now the download on PFG.com is split into an A and a B. My educated guess, that should not be relied upon for a purchase decision, is that it's on B. Also I guess, though I do not know for sure, that getting the DVD mailed to you * would have it all.
* I'm old, and even I don't think the pony express is still operating.