but they were always out of stock no back order.
Generally what this means is "we sold all we had, and aren't planning on making any more, so don't bother to backorder".
Contrary to what the popular press would have you believe, gun companies aren't made of money, and don't make huge profits on individual items. When the press cites millions of $ in profits, they're looking at TOTAL profit from the entire business. What isn't well understood is that each model has to be sufficiently profitable to pay for itself in continued production AND then have at least a little left over for the shareholders.
9mm DA revolvers are a bit of a "difficult sell" in the general market. Lots of people say they'll want one, fewer actually buy. There are many issues involved, some of which are the actual guns, themselves.
There are no DA revolvers "scaled" for the 9mm Luger round. There has never been sufficient demand for any maker to create one. (new frame sizes are expensive). So, what we get (when we do get one) is a .38/.357 size frame, which has "wasted space" in 9mm Luger.
Since you're NOT getting any smaller a gun, many people will opt for the larger (and more powerful and useful) .357, and which works without needing clips.
The history of 9mm DA revolvers has always been, that they sell a bunch when they are brand new and a novelty, and then interest goes pffft, and not enough people buy them to justify continued production. THis has happened, more than once.
DO note that Ruger's convertable Blackhawk .357 with its spare 9mm cylinder has been in constant production since they began offering it, while several DA 9mm revolvers have tried, and failed to endure.
A rimmed 9mm round for revolvers would seem to make sense, but, as Federal discovered (too late) if it fits into an old .38S&W, its not going to be safe, and will be taken off the market.
The idea of being able to use the same gun firing rimless rounds with clips or rimmed rounds without clips is appealing, however, in 9mm the physical size is close enough to fit into some guns made for much lower pressure rounds and that would be dangerous. So due to safety considerations, the 9mm Federal is "obsolete" and no longer made.