You think it might just be hiding somewhere with all my units and stuff? I'll look in the closet... nope, no planet. Pretty sure it just poofed away without a trace! Edit: On second thought it might very well be hiding in the sun...
Strange, planets do disappear if their masses are equal. (Which really really needs a new effect though) But it seems you get the planet impact effect first and then poof, which tells me that the masses were different enough.
Masses definitely weren't equal here, no. The impact concluded and left a crater, then everything disappeared a second later. Really weird bug.