Why are some of my recieved calls not showing on my recent call log galaxy A5

[Andyheapy]

Please help me. I received a call from my ex partner which I answered and it lasted for 35 seconds. I have an app called call recorder and I have it set to record all her calls. The call shows on there and you can hear the conversation but the problem is it is not showing on my recent call log. My current partner now thinks I've deleted the call log to try and hide something. I haven't but have no explanation as to why it isn't there. This has caused a big problem for me. I have a galaxy a5 and this has never happened before. Please help me try to explain how this could be possible.