Where did this bit come from!??

Found this bleed bolt sitting loose:



sitting behind the vacuum pump here:



and noticed there seems to be a hole filled with sealant quite close by (shiny blob next to the vacuum pump mounting bolt) here:


could this be where its come from??


ive had a look in the workshop manual and cant seem to find anywhere on or near the vacuum pump that it could have come from so ahs anyone got any ideas where its from?!

holes filled with silicone are what where used to make the drillings for cam bearings from oil gallery ,if head is 7/16 or 11mm it would be a leak off banjo bolt