I don't think they have the capability to just "write a script that checks for did/did not receive FP rewards" I mean that's the issue with this, is that they don't seem to be able to cleanly identify who didn't get rewards. Keeping records of who did or didn't get FP rewards seems like waste of time, because everyone should get them every day. I'm sure if they had a way to do what you're saying the issue would have been resolved already, And even if they did, I can only imagine that whatever process is responsible for sending out the rewards actually fired, and potentially would have written that rewards were sent in the hypothetical database, but something happened somewhere else along the road that stopped some people from getting their rewards...
This goes along with what I said above, that issues that seem simple to end users (IE: Everything) need to at least be addressed promptly by someone on the team. I get that one of the game sages (I think... he talked like he was one, but he wasn't tagged as a moderator... but it's a new system so who knows) addressed the issue, but that was almost 3 days after the issue was first reported.
Maybe we should look for common circumstances that people who experienced the issue, the only relevant data points that may help the development team nail down the issue that I can think of are
What FP you were in when the issue happened: Gold 1 for me
What Place or bracket you were in when the issue happened: Both days I did not receive rewards I was in the 26-50 bracket of my FP, the issue stopped happening when I started trying again and stayed above 25
Server: 6 for me
And when you usually open rewards(this one seems weird... but I've heard people talk about mail literally disappearing from thier mailbox 5 minutes after it appears... so it might be relevant): I usually open my rewards the following morning, I'm EST so I get my rewards at 10PM, at which point I'm usually at home relaxing with my family.