Ahh. Okay. So, short answer is "there is no way to recover". BUT...
As I mentioned above, any device that has the Field App and has downloaded that survey will have the XLSX. You can copy-paste that XLSX and remake the survey in Connect. If no devices have download the survey prior to you deleting it on the Portal, you are out of luck.
Deleting a survey from the website (or Connect) does not delete it from the Field App. The Field App is designed to work in an offline environment and doesn't check with a server if a survey still exists. The only way you know if a survey you have downloaded is no more is when you try to submit you will get an error.