Yes—this can happen with Ilford Pan F even if the lab didn’t make a mistake. Pan F is known for poor latent image stability compared with many other black-and-white films. If the film sits exposed for too long before processing, the latent image can fade significantly, and on this film even the edge markings may become very faint. Ilford recommends prompt processing; a delay of months can be enough to cause weak or nearly clear negatives.

Slight expiration and storage conditions can also make Pan F more vulnerable. Unlike many expired films, it may not show obvious fogging; instead, the exposed image can simply fade away.

A lab error is still possible in general—underdevelopment or weak chemistry can also cause thin negatives—but based on the film type and the fact it was left for some time before development, latent-image fading is a strong explanation here.