OUR office in-basket has hosted many a baffling letter. But the two-paragrapher that came yesterday was in a class by itself: ''On November 30, 1984, we sent you a press release regarding the new . . . service. Although you were supposed to receive this release, you were not meant to get the letter that apparently accompanied it.
''Therefore, I would like to ask you to kindly disregard the letter and accept our apologies for any inconvenience it may have caused.''
What was that epistle about? Why should it be disregarded? There was nary a hint.
The only inconvenience was yesterday's lost lunch hour. We spent it upside down in our circular filing system, the wastebasket, vainly trying to locate the original mischiefmaker.
The scene is reminiscent of Yul Brynner's classic-in-perplexity, in ''The King and I'': ''It is a puzzlement.''