The user in question will not see any notifications in their inbox, since their last visit to the site was more than 1 hour after the post was deleted (combination of 1 and 2 below):
The only notifications they would see is if comments were made on the deleted post by a moderator, but this was not the case.
The user can access their "recently deleted answers" by visiting their user profile > answers > scroll to the bottom and click on "deleted recent answers":
or visiting the URL
https://tex.stackexchange.com/users/recently-deleted-answers/<userid>. Once they find the deleted answer, they can read the comments.
In this particular case I don't think there's any concern with them not having seeing the comment(s). In particular, they were last seen on the site at
2018-01-05 03:16:20Z (thanks to the Stack Overflow Extras (SOX) script) while the first informative comment was placed at
2018-01-05 02:43:30Z (about 30 minutes before the user's last activity on the site). They surely would have seen this comment as a notification in their inbox. Perhaps they didn't know how to proceed from there and abandoned their quest.
In general it does seem harsh to comment on what is happening, then deleting it and (now) knowing they won't truly understand what's going on unless they dig to find out. However, the following worst case is fairly harmless:
User can't find their post (answer), so they post again as an answer. If they hang around long enough (this is literally not long; we don't have any backlog in our review queues), they'll have an opportunity to discuss things via comments.
Perhaps as a last resort, one could ping the moderators and request they comment on the deleted post, which will then stay in their notifications inbox until it's read.