I have been using a Sony Walkman MP3 player to make voice recordings. I have been transcribing the data using Windows Media Player which I mistakenly thought stored the recordings on the programme. On that basis I had not saved them as document files on my PC. 
Today I accidentally erased the recordings from the MP3 player and also have recorded something onto it. This is when I discovered that Windows Media Player has not stored them as I had believed.
Can anyone tell me if there is any prospect that the recordings might be retrievable in any way from the MP3 player - or are they lost forever?

Today I accidentally erased the recordings from the MP3 player and also have recorded something onto it. This is when I discovered that Windows Media Player has not stored them as I had believed.

Can anyone tell me if there is any prospect that the recordings might be retrievable in any way from the MP3 player - or are they lost forever?
- so I don't know if the files have been overwritten or not.