how to extract deleted 2-D mesh from 3-D mesh

Hello, 

I created a 2-D mesh checked my quality and then tetrameshed it using simple pyramid (by mistake) 

I should have done split quads to trias but i did not.

I deleted the 2-D mesh and saved my file and then realized that i made a mistake by using simple pyramid. Now i am not able to undo it. 
Is there a way to get back my 2-D mesh and then tetramesh it using split quads to trias ?