I made a sandwich two days ago that consists of white bread and canned tuna. I put it in my freezer immediately after making it and it stayed there until today. This morning I took it to work, planning to eat it for lunch, but am now going out for lunch instead. I'd rather not waste the sandwich, so is it safe to refreeze it until tomorrow? It has been out of the freezer for 5 hours and sitting in my desk drawer.
The larger issue is the storage time that the sandwich has already been subjected to. 5 hours at room temperature is enough time for at least some of the tuna to spend significant time in the "danger zone" (the temperature range from 40 to 140 degrees F where bacteria grow most quickly).
At this point I would not consider the sandwich safe, regardless whether you refreeze it. Refreezing will not render it safe again and I would recommend tossing it.
When you freeze anything that contains moisture, freezing produces ice crystals that rupture cell walls; this damage speeds up any spoilage that might begin. The more often you freeze a food, the more damage is done. I would advise against re-freezing anything you plan to eat without cooking, simply out of concern over not knowing how quickly any spoilage will progress as it thaws.