What happens to the QBT that you leave on Cryptopia Exchange?
Basically nothing.

But...
In case your Cubits are on Cryptopia, you will not be able to sign a message (as the address is owned by Cryptopia).
If you want your SCIFI share, you have to move these coins to a local wallet (your address, you can sign it).
With other words, if you want some SCIFI, you should:
1) Move the QBT from Crytopia to your local wallet before February 1st.
2) Send your (local wallet) address and signed message to vampirus.
3) Wait till you received your SCIFI.
4) Send your QBT back to Cryptopia if desired.
5) Enjoy your new SCIFI.
Excuse my ignorance, but how do you: 2) Send your (local wallet) address and signed message to vampirus.
Is it a message on bitcointalk or a signature you generate from the command line?
If it's a command line signature can you give instructions on how to do that on the wallet?