Fermi-LAT upper limits on the integrated energy flux above 100 MeV for different exposure times, compared with the best-fit optical energy flux from Zimmerman et al. (2024) in black. We note that observations for ΔT = 7 d are less constraining than ΔT = 5 d as a result of having a larger TS value, although they are still consistent with a statistical fluctuation (see Appendix A). The grey vertical line indicates the arrival time of the best photon triplet candidate.