TEETHING - tooth vanished?!!

My lo is 7 months old, had this white line on bottom gum for a few days it went away?!! Then came back bigger but now it’s gone away again. Nobody believed of course but I did take a photo, thankfully - to prove my sanity 😂! Is this teething? I got so excited he was cutting a tooth but its been a week and nothing since the first appearance of the mysterious white line, it wasn’t spikey either couldn’t feel anything just saw it - he was also SUPER grumpy 😆. Thanks ☺️