Money disappearing from my account without a trace

Yesterday the 28th of November 2022 at 09:01 am R160 was withdrawn at Riordan & co and balance at that time was R279. The following morning 29th of November 2022 I check my account as I always do and my balance was R262. I check my transaction history and nothing. R279 - 262 = R17. Where did that money go???? I used the FNB chat but to honest no idea what that's actually for. In all the time I tried using them it has proven useless. I want to know what happened to that money. How can it just disappear like that. Because then I can't trust my money in the account I'm using anymore!