Appreciate the extra context.
in essence, no. the CommServe will think that data is there (unless you rtun a Data Verification, which run against a Cloud library might incur charges, FYI).
What you would do is browse and restore by Job ID from a range where you know these jobs are valid.
Now, if you have Aux Copies of the data going to Tape (or anywhere else, really) and those libraries are safe from this disaster, then you would be 100% fine (persuant to the Aux copies being caught up, etc.).
The only way for the CS to 'know' what is valid or not would be to look at the actual data compared to the job IDs in the database and verify that the Archive files (that make up the jobs) are physically there, which is what a DV does. As you noted, it's a time consuming process if done at a large scale, so you only do it when you need to like this situation.
Let me know if that clarifies things for you!