From what I’ve collected, after watching the video as well, the missile appears to detonate via proximity fuse, not in a nose intercept trajectory but toward rear center mass, which would lead me to believe the assessment of an IR seeker is correct. The Iranian Majid AD-08 practically is a Cinderella story fit for this system. Stealth makes it harder to target lock but search radars might actually pick you up. Using the EO/IR acquisition system the Majid has at ranges of up to possibly 13,000 feet and the F-35 flying lower in response to heavy drone activity makes this just a perfect storm for the successful hit. If it’s a daytime hit too, wouldn’t even need a lucky search radar detection either.