However, I'm sure some quick checking on actual aircraft movements into SIP very early on the 8th would soon eliminate any doubts, or confirm what they saw.
According to Flightradar24 for that time, the only a/c anywhere near Kelantan was a Chinese Eastern Airbus (MU5093) which was at 37,000ft. So unless another plane with no transponder was in the air, there was nothing else for observers to see.