This would fall under data recovery from storage device. When data is deleted the space allocated to the data is made available to be overwirtten. When an operating system is on and active, it continuously writes new data the drive as part of its background operations. This data might be small but it is written to available space, therefore there is a chance it might overwrite any deleted data and cause the permanent loss of that data. As such the data will become unrecoverable. This process is a bit different between SSDs and HDDs but also similar. Therefore it is very important not to use the device or turn it on, so to protect the deleted data on the drive.
In the case of android, i don't know how much data it writes in the background. Might be less than desktop, but you really should keep the phone totally off if you want to do any data recovery. Don't use the phone at all.