sdCard is sdcard0, which is internal storage, it's not a physical SD card. extSDcard is the external card, mounted as sdcard1. Phones don't normally come with external SD cards installed these days, just sdCard which, as I said, is just a folder in internal storage.
As for recovering deleted files (it doesn't matter how you deleted them), the free version of
DiskDigger undelete (root) recovers picture files, but as it says, the phone has to be rooted. Rooting writes to storage. Installing writes to storage. And
anything writing to storage can overwrite all or part of a deleted file. (This is why backing up was invented - so you always have a copy of your important files.)
Recuva works on the PC's drives, it can't work on a plugged in phone's storage. (It needs access to the drive's directory, which it can't get from a plugged in Android. DiskDigger, running in the phone, can. And no, you can't undelete on a Linux-based system [which Android is] without root.)