Facebook messenger question - please help

In my facebook messenger app, when you open it and it has all the people you've received messages from, against one persons name it says I received a message yesterday, however when opening up the conversation thread with that person it shows the last received message as a month ago. The persons conversation is in order as though I received a message yesterday however clearly no message received. Has anyone else experienced this? Could it be a facebook glitch? Would appreciate any suggestions