Are you willing to do something destructive? Remove the epoxy packaging and look at the chip. For a popular part like an LM317, you can probably find a picture of a genuine chip (maybe as they were made 40 years ago). Otherwise, you could compare it to a known good part.

Some manufacturers have active programs to find counterfeit parts and libraries of information ueful for identifying thenm (like the way the logos and the numbers got printed). You might contact them with pictures of the packaging and the silicon chip.

My buddy at Intel told me that one of the common problems is "NOS" Mil-spec versions of obsolete parts that were really repackaged pulls. They often seem OK, except that they have a higher wear-out failure rate (apparently, catastrophic infant mortality failures are relatively rare, as are the completely wrong chip which had been re-marked).

A priori, I would not automatically assume a failure at 1.3A instead of 1.5A was sufficient evidence, especially in a "new" design with no history of proper cooling, etc. You might have a case if it failed in a known and mature design.