"Hidden" messages in Motorola messaging? Phone info:

Motorola

Model: Moto E, 2nd generation

LTE: 4G LTE

Operating system: Android, version 5.1

Let me know if any more info would be helpful.

Issue:

My phone's Messaging app (the one that comes with the phone) seems to be "hiding" text conversations sometimes. It'll show how many unread messages I have, (see attached image, the circled number), but I don't see any conversations with unread messages shown. I know there are some conversations missing, I just need a way to un-hide them. As far as I have found, the only way to un-hide these conversations is to search for the conversation by contact, but this only works if you know which contact's conversation was hidden. Any thoughts on how to un-do  this, or what is making the messages hidden? 



My research:

I've looked on Android support sites, done Google searches of 'Motorola hiding messages', and all sorts of related searches. Unfortunately I have had trouble finding anything besides suggestions on how to hide messages.
Partial answer (OP may update with findings later)


From my experience of Moto X Play messenger app - the count corresponds to unread messages.
OP is unable to identify unread messages. Proposed solution:


Use SMS backup &amp; restore to take the backup in xml format and open it on PC (browser, notepad or any other program) and compare with messages on phone to identify "hidden" messages. OP has been able to identify two so far
and  in the process of identifying other two.
Find out what is special about those SMS originators. Guessing, they could be contacts saved on SIM, or social media contacts or Google groups /Hangouts or contacts marked spam, blocked/ unknown contacts for calls, carrier messages or.... 
Once the nature of contacts is identified, take steps to treat them as other contacts whose messages are not hidden.