...you know what hit/s you.

Hit.
Then carry marmalade in pocket.

Sounds messy, but yes, 'hit'.

Thanks, neologist and roger.

Could you let me know why since all the other verbs are in present or future tense?

Thanks, neologist and roger.

Could you let me know why since all the other verbs are in present or future tense?

"hide" is conditional and a future possibility. Anyway, that's my best guess.

We use the phrase standard phrase 'before you know what hit you' to say that an event which happens to a person directly does so with no warning or very suddenly. For example, if you touch a 100,000 volt power cable you would be dead before you knew what hit you, likewise shot through the head. You might say to a colleague "If the boss catches you slacking you'll be fired before you know what hit you". To use it about some remote and not at all sudden event that does not drectly impact you like someone finding and eating marmalade is not really appropriate.

Thanks, Tes yeux noirs and Roger.

Thanks, Tes yeux noirs.