You can't fix stupid, but you can fix careless
This is a good example of UX tradeoffs.
You could fix the recovery problem by asking for a secret question, mobile phone number or additional identifying information.
But before you do that, are you sure you're solving the right problem?
- Consider the cost. Asking for more information creates more UX friction for your app. Let's say 5% of your users mistype their emails. If you ask for more information at sign-up, you are creating additional friction for 95% of your users just to handle the 5% of careless typers.
- Have you solved the upstream problem? Addressing account recovery is a downstream problem caused by upstream carelessness. Users entering account recovery are already frustrated, so if you can avoid a recovery situation to begin with, that is going to be a MUCH better experience for users.
Here's an approach to improving the upstream problem:

Get users to enter their email address more accurately by:
- Prompting them for a confirmation.
- Disabling cut and paste on the confirmation.
- Explaining why accuracy is important.
This may help solve the upstream problem for careless typers. There will always be a tiny minority of users who will still mistype their names, but you cannot let the "tail wag the dog" by creating hurdles for the 99% just to serve the 1%. At some point, you can fix careless but you can't fix stupid.