have you got a computer ?
if so go to www.gmail.com and log in with the same google account the nexus uses and see if they show up there.
if they do you should be able to restore them to the nexus
please let me know if they are there or not and i can get you further instructions
ok can you export them to a csv file please and save that on your computer. that will keep them safe and then we can try to sync it back to your tablet
sorry i am with another customer and i probably ccant get to you for another hour or sometime tomorrow for the phone call
on the tablet
go to settings
MAKE SURE IT IS THE CORRECT GMAIL ACCOUNT
click on that account
click contacts and it should say sync off
click it again and it should say syncing now
that should bring them back down from the google server if they were there when you looked at it on the computer
it may take a few minutes
i only had you download the csv file as a precaution
then you just had to resync
i dont know what you did with your contact app to start with. i assumed that you deleted the contacts off the tablet. if you had just installed another contact app that didnt work i would have told you to uninstall it.