Is there a way to use the same webform for anonymous submission and for back office queries, i.e. hide existing contact box for anonymous
In your webform, add a hidden field called Role


set the default value to the token [current-user:roles:first] 
set the type to 'Hidden element'  (Secure value looks like it should work but didn't in my test.)


Then on the Conditionals tab add the rule:

If Role is anonymous user
then Contact1: Existing Contact isn't shown