Lufthansa — Cancelled ticket

Hello. In august, I was ticketed to fly on Lufthansa and return to Los Angeles from Italy. When I got to the counter, they had no record of my reservation. Therefore, I had to purchase a new ticket on the spot. The ticket was booked through expedia though upon departing in July, I had to switch the departing date due to covid. It was NOT to affect my return, but it did. Expedia is blaming you and you guys blamed expedia when we were returning home. Now, we are out over $3000. My name is Lawrence Golin. I was to return on August 3rd. the ticket number was[protected]. Please help and let us know if you are dealing with expedia on this.They are claiming they are talking with Lufthansa. My cell is[protected].