Greetings,
Because your bicycle was stolen from your home, the theft is covered by basic household insurance. That applies even if the bicycle was stolen from your garage because the shared garage of your apartment building qualifies as part of your home. If your bike were stolen outside of your home, it would only be covered if your policy included an optional rider which covers "simple theft away from home". E-bikes require special insurance coverage.
Whether or not you must keep your bicycle locked in when parked in order to maintain insurance coverage depends on where the bicycle is parked. If you were to park your bicycle on a public street without locking it and your bicycle was stolen, you may not be reimbursed for your loss. But keeping goods held on private property under lock and key is not generally required in order to maintain coverage. This applies to goods stored in your cellar, for example, as well as those stored on other private properties like your workplace or the homes of friends and acquaintances.
The primary requirement is that you report the theft to the police immediately and then report it to your insurer.
You can find out more in our guide to insuring your bicycle.
Best regards from Moneyguru