Do you have access to your Bitcoin private key or not? if you had access then why would you use a third party and unreliable wallet like Waveslite client?
He probably wanted to buy some tokens or waves into the Waves decentralised exchange, so you do need to send your bitcoin into it if you want to trade. There are a number of possibilities like wrong copy/paste, slow transactions, ... potentially it could be anything. Now, the last thing I would think about is that the Waves platform is taking people´s bitcoins.