why did he lie???

So tonight I saw a girlfriend to plan some stuff for my upcoming baby shower. My SO text me to say he's popping out for a drink with a friend and would message me when he's home. Whilst he was 'out' he needed to transfer some money from the joint account as he is low and put most of his wages into the joint account this month. We are due to complete on buying our first house together on Monday. Anyway.... I have him on find friends and he didn't go out at all. He was at home all night. He messaged me telling me what pubs etc he went too and has gone into rather a lot of detail but he never went out!!! I don't want to sound like a physco and say I stalked him but it just doesn't add up. Any ideas????