A story both SF and Fantasy where a character in a spacesuit has a phantom arm

I don't remember when I read this. At least 20 years ago but maybe more. Nor the length. Probably not a very short short story but whether a novelette or a full length novel I have no idea.

It was at the same time SF and fantasy, because the only thing I remember is that one of the characters, while in a spacesuit in the vacuum (SF!) was able use his "phantom-hand" (Fantasy!).

I think that at some point he had lost an arm and developed this strange telekinetic power which he interpreted as a "ghost arm". Later he was grafted an artificial arm, but retained his telekinetic power as a "third" arm that could penetrate matter and for instance wipe his sweat from his brow while in his space suit. I don't remember anything more, alas.

Answer

I bet this is Gil the ARM, protagonist of a series of short stories by Larry Niven, collected as Flatlander (1995).

Gil, who works for a law enforcement organization known as ARM, lost his arm in an accident, and before he received a transplant, his latent esper talent manifested the symptoms of a phantom limb as an actual psychic appendage he could use. (Note that the new arm was a transplant, not a prosthetic.)

You may be remembering a reminiscence in "Death by Ecstasy" where he describes learning to use and live with his "imaginary arm":

I found I could reach through a cabin wall to feel for breaks in the circuits behind it. In vacuum I could brush dust from the outside of my faceplate.

At one point he is tied up and smokes a cigarette by grasping it in his "hand." Later in the same scene he reaches inside his captor's chest, feeling the surgical scars on the way in, and grabs his heart to stop it.

The only other story where Gil wears a spacesuit is The Patchwork Girl where he's solving a murder on the Moon. In this story he uses his "hand" to "feel" a hologram of a real moonscape, sifting through a pool of dust to see if anything is hidden there. (His imagination limits his esper talent to the shape and reach of an arm, but it is capable of analyzing something by "feel" that is not actually present as long as it appears to be "in reach.")