you might wanna try actually contacting support,not posting in the forum.
Steam is problematic so if you trusted there services to only download from a bigpond server you have been fooled.
Think you'll find Steam and GA are not linked. Steam just downloads from what it percieves as being a GA download host, if it can't find the download you wanted it may well have chosen a different server for part or all of your downloads which is not GA's fault, that's a steam issue.
The other issue is if you have viruses so often there's something wrong with your connection or software. I can't remember the last decade i had to redownload everything because of a virus. Lucky i guess.
You can just backup the Steam folder too, you don't have to reinstall all the games everytime, just install the base software then copy over it with the backed up folder. hell it even has it's own backup process for installed games you can use
Oh well live and learn good luck with your problem