Another user suggested on Portuguese Wikipedia that when a page is deleted, its author should be notified:
https://pt.wikipedia.org/w/index.php?diff=36928268&oldid=36926057
Using the terminology from
https://github.com/wikimedia/mediawiki-extensions-Echo/blob/08fc83b6de1feb58231834864cb9caa2004e0b04/Echo.php#L423
what we need is a new event for page deletion.