Related for Sotah 90:3

[If a farmer] took a sheaf in order to take it to the city, and [then] he put [this sheaf] down [on the ground] on top of his friend (i.e. another sheaf) [while still in the field] and [then] he forgot both of them [in the field where he put them down], then the bottom [sheaf] is [considered to be] Shikcha (forgotten sheaf), and the top [sheaf] is not [considered to be] Shikcha. Rebbi Shimon says, “Both of them are not [considered to be] Shikcha. The bottom [sheaf is not considered to be Shikcha], because it is covered [by the top sheaf], and the top [sheaf is not considered to be Shikcha], because [the farmer] acquired it [for himself].”