As in, how many times have you:
Used up 1 (ONE) bomb, despite having more than 1 in stock, AND also heard the Pichun sound that indicates that you have actually deathbombed, yet you somehow managed to do it in the 1 frame (
1/60 of a SECOND) period that allows you to deathbomb using only 1 bomb as opposed to 2.
In my 50+ hours of playing, I did it roughly about 4-5 times. So if we are begin generous, in my case in average it happened ONCE every 10 hours!

(Pretty damn rare!)
Also not sure if these are the actual numbers, but pretty sure I remember reading here than the period to deathbomb with only 1 bomb was exactly 1 frame, so..