Hi there!

This is certainly not expected behavior. Premium subscriptions are completely voluntary and NOT required to continue using ABP for ad blocking. I'm terribly sorry to hear that your custom filters were deleted. Back up and sync is a feature we are working on making available. In the meantime, we advise saving a copy of your custom filters in text document. Feel free to reach out to us via support@adblockplus.org.

Thanks
Shannon
ABP Support Team