Man, my heart goes out to you. 
Read the "published a report" link in our
Is It Legal to Copy web page. We paid a Lawyer group that stands for Consumer's rights to do the research for us in WestLaw and NexusLexus legal databases. They came up that, based on past court cases and rulings, it is most certainly legal to copy your discs to a hard drive (and make back disc copies).
As you have identified, the problem is that you don't have proof of purchase any more. If I were you,
RIGHT NOW... TODAY... (as in URGENT!!!!!!) I'd contact the distributors and producers you bought from, they can pull up your customer record and see what discs you bought, then print a new set of Packing Lists for you. I expect they know exactly which CDG discs you bought by Brand-DiscID number. That's the only way they can have a Warehouse staff pull the right product and send it to you.
MAKE SURE you keep all the Police Reports and Insurance Claims of the thefts.
If it were me, I'd rent a Bank Lock Box and secure these reports in it... TODAY... LIKE WHY ARE YOU READING THIS??? 
If you have listed the CDG discs on those reports, that is a good start IF... "The Man" ever tried to take you to court.
The only time a Host (who was not outright copying and selling illegal discs) was taken to court, the Judge threw SC out of court because it basically was a frivilous suit. They will not likely try this again.
What normally happens is "The Man" demands the Host to sign an agreement to never make backup copies again.
DO NOT SIGN THIS as it converts Copyright Law to Contract Law, and Contract Law is much easier to sue on. This is shear intimidation with only the "threat" of a law suit behind it. If you
ARE CONFIDENT and you have
NEVER EVER EVER copied a CDG disc you did not buy, then if ever brought into a Court, you can stand tall and look the Judge square in the eye and tell him you have never obtained a song illegally.
BTW: That goes for downloading mp3+g songs for free and converting them to .bin files and burning them to a CDG disc.
That is illegal also! Think about it, if you do this even ONE TIME, you KNOW in your heart that you stole AND... you will NEVER forget that... EVER! 
You can never look a Judge in the eye and san I NEVER HAVE... after that. Don't EVER GIVE UP YOUR HONESTY OR YOUR INTEGRITY!!! 
You lose your HEART as soon as you do. 
As to bringing in a US Marshall, to my knowledge... and I am not expert, but have talked to Sheriffs, and Attorney Generals in various states... who DO KARAOKE THEMSELVES, we have consistently heard that the US Marshalls come into play AFTER going to court and the Judge orders them to confiscate your equipment. I am all but positive that you will never see "The Man" come into your show with a US Marshall without your first having been in Court. You don't have to tell "The Man" anything. He is trespassing at your venue and the Bouncers there have every legal right to throw him out the door.
One Host who was harrassed by an ASCP Collector told "This Man" to INVOICE ME. "This Man" demanded immediate payment on the spot and prevented the show from continuing. The Bar Owner called the Sheriff, who immediately showed up and escorted "This Man" out of THE COUNTY!!!
The Sheriff was not too happy with "an outsider" coming into His County and harrassing His Tax Base Customers. Get the picture? Follow the Money and you'll see who truly will take the time to harrass you. If you are above board in all your dealings, I'd be VERY suprised if you ever were even harrassed.
DON'T feel guilty if you aren't. I repeat... DO NOT FEEL GUILTY IF YOU AREN'T!
CONFIDENT HONESTY RULES............