It is a new forum, so I am not on a vps which would have handled this without question.Doesn't sound like a lot of traffic but the only metric you've given is I'm guessing unique visitors. You say less than 24 hours. So about how much less. If 17K hits occurred over 12 hours that would be an average of 24 per minute. Which is absolutely nothing.
My usual benchmark for configuring a low end vps for Xenforo (5 dollar a month digital ocean, linode, vultr) is 250 users per second at 1000 requests per second. At that exact rate you could rack up 17k visitors in... Is my math right 68 seconds?