But absent success with the attorney, it's not BS at all that no record exists.
Not an attorney and am not familiar with CT but have some experience with other states and how they handle expungements. Understanding this may be quite different.
For other states, the local courts do tend to retain records even after expungement (this does not require a conviction). After expungement, records are impounded with an order for the other state agencies to delete evidence that the case had ever existed (which may require some legwork) ... it's 'deemed erased'. This may include things such as arrest / charging information, fingerprint blotters, photos, notes, etc.
Re-offenders of the same offense(s), sometime later, may see such past problems re-appear in state courts in some circumstances. But the LE will no longer 'know' about it until such time (exceptions are the hints from the breadcrumbs).
The clerk may deny that such records exist if asked (deemed erased). To get to the records would require a judge to sign off on a request. LE can petition the courts for responsive records in some limited circumstances. E.g. background for security clearances.
The problem with expungements is that the individual may have a court order for the other agencies to erase related records they retain ... but it's not necessarily automatic ... state-dependent. An individual has to petition each of the state agencies with the court order to have them remove the information and along with the other breadcrumbs (potentially).
Personally, with a limited understanding of CT, I'd look into pursuing a request to the courts for access to the records. And, if not already done, petition the state criminal justice department, sheriffs department, county and local police departments, etc with a copy of the court order to ensure that they delete any associated records. The later may be enough to remove the breadcrumbs, idk. But, of course, you need a copy of the court order.
This could be an avenue to look into.