All is not lost. There are many utilities that can recover deleted images from a memory card. There are even some free ones out there. Here is one that appears to be genuine. (I have never used it.)
What OS are you using? Were you watching the import process as it was happening? Did it complete? Were there any errors that were reported, such as the files were damaged? Can you look at the intended storage location for the files on import to see whether the files were saved?
Hopefully, you have learned from your experience never to use the option to delete from your card before you know that the files have been properly saved.