Turns out my Steam account is hacked for good this time, last time it was only blocked and got magically unblocked. Just this time it's not existent anymore AT ALL.

Think writing to Steam won't do, the email was unverified and has probably already been changed.

Luckily enough my backup account sill works that means I atleast still have the Orange Box that a kind member here gifted me last time, thanks again!

Losses:

CS:S
DoD:S
Shattered Horizon
Mass Effect
HL2:DM
Garry's Mod
and MODERN WARFARE 2

not that I care much about MW2 anymore but I have the disk version and that will now be useless anyway or think I can proof with that MW2 Key alone that the account is mine?

Interestingly enough this happened very shortly after I verified my Steam account on garrysmod.org....