Not adjacent, which is next to, but going in the third dimension. Note the immediate implication of the existence of subjacent. This was borrowed around 1610 from Latin superjacēns (in its stem for superjacēnt-), the present participle of superjacēre, to rest upon, from super-, above + jacēre, to lie upon.
In the third room, immediately press left and up together to collect the superjacent coin, and then get the rest.
---L.