Tile scan. Sorry.
EDIT: OOOH! Unless you can use the item "Dirt Patch" that drops from Oaks.
Unfortunately, it's gotta be a tile scan, as I already tried the "Dirt Patch" from Oaks, having had the same thought myself...It says something about wanting fresh dirt, as I just tried it again to see what the message was...
Although, the tile does seem to have a unique ID, so after you find it the first time, I guess it could be stored as a persistant variable to make it faster/easier to use later. Doing a finditem on the item ID only yields 'X' as the item type, so that doesn't really help.