Sometimes I get more threatening letters than the average divorce lawyer.

Like the one from a reader accusing me of publishing unsubstantiated rumors and “demanding an apology.” Or the letter last week from the El Monte, Calif., office of the Internal Revenue Service that began with, “We selected your federal income tax return for the year shown below to examine the items listed at the end of this letter.” And there was the second notice from 3Com that asked me to return my evaluation Palm Pilot III.

The third one hit me like a slap in the face. Mad readers and IRS auditors I can deal with. The problem with returning the Palm Pilot was that I didn’t want to and – more important – I couldn’t. The PDA was MIA somewhere in my office.

A couple of years ago I wouldn’t have had this problem. Laptop computers weighed as much as today’s PC towers. Cellular phones were as bulky, and heavy, as a brick. Personal digital assistants were more cumbersome than a college dictionary. You couldn’t misplace these things because they were too big and obtrusive.

Not today.

PDAs now look like calculators. Phones are often mistaken for chocolate bars. And portables are – well, portable. It’s easy to lose these things.

“I’m constantly misplacing my cellular phone,” says Lillian Glass, an author and psychologist in New York. “It’s so easy, because it’s so small.”

On her way to a recent appointment in Los Angeles, Glass got lost and reached for her cell phone to get directions. She thought she had brought her phone along, but when she rummaged through the glove compartment, she found a tape recorder instead. “The tape recorder and the phone were about the same size and shape. It turns out I had left the phone at the office and taken the tape recorder by mistake,” she recalls.

Cell phones have a tendency to blend into the scenery, as consultant Lorraine Sileo discovered on a recent trip. Her Metro North Railroad train broke down between New York and Brewster, NY, and the crew had to evacuate everyone, she remembers. “I was talking on the phone when they started emptying the train,” says Sileo. “So put my phone down, gathered all my belongings and left. When I got home, I discovered I had left my phone on the train.”

Fortunately, Sileo recovered her phone the next day. But, she says, “it was an easy thing to do. The phone is black and it matched the seat, so I couldn’t really see it.”

PDAs get lost with the same regularity, says Stephen Froelicher, the chief executive of Pilot Island Publishing, a peripheral manufacturer for the Palm Pilot. He’s had his digital assistant swiped from him at a restaurant but says that getting one stolen is often the last thing a traveler has to worry about.

Size does matter to the PDA, he says. Or lack thereof. Froelicher’s tech support staff reports two strange stories about lost Palm Pilots.

In one, an Arizona motorcycle rider hit a bump on his way to work and out popped his Palm Pilot. The machine was recovered hours later, roasting in the desert sun. A Florida user inadvertently dumped his PDA with what he thought was an empty plastic bag. He had to dig through the trash later to find it.

Although it’s impossible to say how often these gadgets get lost, I’m certain that it’s a painful thing every time. I base that observation on the first-hand experience of trying to track down my lost Palm Pilot and return it to its rightful owners at 3Com.

I tested the Palm Pilot last fall before moving to a larger office. My biggest fear was that the device had somehow gotten tossed into the recycler along with the several hundred-odd press kits stored in my closet. Following hours of futile searching, I figured I’d call the folks in the Palm Pilot division and throw myself at their mercy.

But then my writer’s instincts took over and I decided to procrastinate. I waited several weeks, hoping that maybe 3Com would forget about the loaner and leave me alone. That’s when, much to my relief, I found the gadget hidden among boxes of software and mailed it to them before I could lose it again.

What did I learn from this ordeal?

Well, that sometimes smaller isn’t better. That while black may be a discreet color for a PDA or cell phone, it isn’t always the most conducive to locating the darned thing. And that next time I request a loaner, I’ll find some way to permanently attach it to me, as Pilot Island’s helpful carrying cases do.

Look out, Dick Tracy.