I recently contacted support about this and was amazed to find that what I thought would be a simple function doesn't exist.
We have had staff leave recently and not so recently and have had requests from senior management to look for data that they may have stored in sheets that they may of owned or shared or transferred with someone else prior to leaving. I'm not a big user of Smartsheet, but was amazed to find that there is no way to perform a simple search for all sheets within our organization and be able to access them without them being shared. This is a basic administration function.
I was advised that a Sheet Access Report can be run, but this isn't really the same thing so maybe this can be a feature request?