Just as it looked like the iPod-related class action suit against Apple was getting interesting, Eddy Cue arguing that competing music stores had effectively hacked the iPod, it now seems the case is in danger of collapsing.

Apple’s lawyers have written to the judge to say there is no evidence that either of the two plaintiffs owned iPods during the time affected by Apple’s action to remove non-iTunes songs from iPods … 

The NYT reports that Apple had checked the serial numbers of the iPods owned by the plaintiffs and determined that both were purchased after the period affected by the class action.

Both plaintiffs claim they purchased other iPods within the qualifying dates, but Apple has been unable to find any record of these models. The company’s lawyers have asked for proof of purchase to be produced.

The class action seeks damages for iPods bought from September 2006 to March 2009. Apple said it checked the serial number of Ms. Rosen’s iPod Touch and found that it was bought in July 2009, months after the class period ended […]

Apple said it verified that an iPod Touch was purchased by Ms. Tucker in August 2010, also outside the class period.

U.S. District Judge Yvonne Gonzalez Rogers said that she would research the matter herself, but the case could be halted – temporarily or permanently – if the issue couldn’t be resolved.

Judge Rogers asked attorneys to promptly suggest a next move, telling them that she was not interested in waiting.

“I am concerned that I don’t have a plaintiff,” she said. “That’s a problem.”

The court had earlier heard video-taped testimony from Steve Jobs, with a snarky comment about rival music store Real Networks, asking “Do they still exist?”