size lost within a short period of time should also be able to be put backed on within a short period of time.
if u lost the muscles in 4 days.. u shd be able to get them back in ....uhhh...1-2 weeks i suppose (i'm just guessing)
yeah, its still a setback, but i dont think its as bad as it seems.
regaining muscle lost not too long ago isnt as hard as packing on new muscle mass which u never had before.
meaning if youre 65 kgs, and wanna gain NEW 3kgs, it would be much harder than just 62kgs regaining to become 65kgs.
cant remember where i read this tho. my 0.02

also, like darklight said, in my own cases, i tried forcefeeding to minimize muscle loss during sick periods so the setbacks arent as bad.