Hi,
Once you block someone on iPhone, their texts don’t show up in your Messages app at all.
Apple doesn’t keep them in some “hidden folder” that you can open later — they’re just not delivered to you.
I learned this the hard way after blocking a contact and then unblocking them later. None of the messages they sent while blocked ever came through.
If you unblock the person, you’ll start receiving new texts from them again, but you won’t see anything they sent while they were blocked.
There’s really no recovery option unless you had a backup from before you blocked them and those messages were already on your phone.
So basically: blocked = gone. The only way around it is to check with the person directly and ask them to resend anything important.