OK, so the first 2 times my Gravisuite dissappeared, I thought it was some wither skele magic happening. After Building my 3rd gravi, I just got hit by a creeper explosion, boom, chest gone again. Cannot keep building these.
There was a bug in 1.5 with ic2 stuff disappearing when the energy level dropped towards 0. Can you recall the energy level at the time they disappeared?
The bug still exists in IC2 experimental haven't been on TDT in a while but whenever quantum armor excepting the leggings ran dry it disappeared
This problem also exists on the Resurrection server. Only ever had the Nanosuit armor go poof on me, at zero charge, though. Mah quantum suit I ENSURE stays above 60%. Enchants also go a long way to preventing IC2 Armor Poofing, until the IC2 crew can get this issue fixed and pushed to servers.
I had prot IV and soulbound enchants on the gravi. I am certain this is not a damage issue, I kept them pretty charged regularly.