"Even if I show old records?"
What do you have? Your question was "how do I prove it was mine". If, when asked, the only thing you have to say is "I know it was mine", then I would assume you don't have anything.
What kind of records are you talking about? What were you using the domain name for? How would you show anyone that the domain name didn't expire, and what is your answer to the question, "Why didn't you do anything for two years?"
A lot of domain hi-jacking / accidental deletion issues can be dealt with in a couple of phone calls, if dealt with promptly. In this instance, you'd probably have to do a lot more than that. But, sure, you *might* get someone's attention if you want to drop a couple of ten G's on a lawsuit. The question really is, "What are you willing to do to prove it?"
Does anyone here know if your unidentified registrar maintains archived records for that long? Not likely.
Let me re-phrase my question above to, "What would you be able to show me to convince me that the domain name had been yours?"