When coffee prices soared, people began switching to alternative drinks. One of those alternatives, a cereal drink called Postum, began disappearing from supermarket shelves as rapidly as clerks put out fresh supplies.

District Liners sent me letters saying they suspected (and in some cases actually alleging) that General Foods, the manufacturer of Postum, was cutting back on its production of Postum because "there's more profit in coffee," which General Foods sells by the ton.

You may recall that in response to these letters I made some inquiries into The Great Postum Plot. The people at General Foods told me they were turning out as much Postum as they could (far more than ever before), and that they were working on a plan to expand production which they hoped would show results within a matter months.

A reporter learns to file this kind of response in his "Interesting If True" folder. To check it, I talked to local supermarket officials.

From them I learned that they are now receiving and selling about three times as much Postum as they were a year ago. This, it seemed to me, was the best kind of proof that The Great Postum Plot simply doesn't exist.

Now, however, word is out that General Foods is bringing out a new product that blends coffee with "extenders" of various kinds, and this has given The Great Postum Plot new life. Readers are again suggesting that an investigation of General Foods is in order, to find out whether the company is holding back shipments of Postum to "force" people to buy high-priced coffee instead. As one woman put it, "How come they have the factory capacity to develop and produce a brand new product but can't fill orders for something we have come to depend on?"

Several logical answers to that question suggest themselves, but I doubt that this reporter is in a position to get at the truth. A congressman empowered to subpoena witnesses might get some accurate testimony on the subject, but I am prepared to wager one strawberry ice cream soda that even a congressional hearing wouldn't turn up any evidence of a plot to hold down production.

My guess is that an investigation would reveal little more than the usual pattern in these cases.When Postum began getting scarce, people started laying in reserve supplies whenever they saw it on display. This created an artificially high demand that no rational supply system could satisfy.

As we all know, when you and I lay in a reserve supply of a product that may soon be scarce, we are merely being prudent and foresighted. But when other people stock up, they are hoarders. Especially if they do it before we get ours.

One day soon, I suspect that your supermarket's shelves will be stocked with more Postum than even the hoarders will care to buy. The magic moment will arrive the second time shoppers see a good supply on display with nobody running toward it to load up his shopping cart.