A contact sent me a message, but I never received it#
The most likely scenario here is that you weren't connected to the network. Even so, you should pick up the message when you connect to the network again.
Messages do have an expiry of 7 days if they are not collected, so it may be that your device was not connected or was out of battery for an extended period.
If you are seeing this consistently or believe that you were connected and should have received a message, please contact the SafeTrx support team.