The last time I saw a thread about this shortage was in March. I had 1111 Salvage and 7 Prototype at the time.
https://forums.galaxy-of-heroes.starwars.ea.com/discussion/comment/1819692/#Comment_1819692
I can definitely see how some players could find themselves short of the Salvage. Since March (8 months!) I have added another 23 g12 to my roster and my Salvage supply has dwindled to a mere 680 pieces, with a small pile of 156 Prototype sitting in reserve, which means my net Salvage reserve is only 500 pieces. Still not feeling the shortage as acutely as some do, but I can see how it could be an issue for those who gear at a more spirited rate than I can manage.
The fact remains that Salvage are available in shipments, I've seen them in the Shard Shop for one. If you've run out, you'll just have to treat them as a rare commodity like stun gun salvage and snap them up whenever you see them.