Potential Selling Bug? - Also First Post

Just a backstory to start off with - Was planning to give Frappuccino 300 diamonds since he was "salty" about me raiding his vault, and perhaps in the long run to establish a better connection with Vanta considering that they just raided my newly created farm (Thanks Graff, Speedcell, and Frapp LUL). I asked him to meet me in spawn to complete the exchange. Many people were following us around, presumably wanting to steal my diamonds when going to exchange them to Frappuccino. Thought of an idea to sell them on the market for free, in order to prevent anybody else from getting in our business and stealing the diamonds. I did the standard selling procedure, listed 300 diamonds, and then put a price of exactly "0" for all of them. The message that came up when I entered "0" was "Price was be greater than o!!". And just like that all 300 diamonds were gone, 5 - 6 hours worth of mining. I've tried getting them back by re logging, clicking on the cancel button, but nothing worked so far. I've tried selling other materials as well for free, and they all come up with the same message and consequence, they disappear entirely.

Is this a bug? The listings for my shop didn't show up when I looked at what I was currently selling. I'm not entirely sure what happened here and I would like a reimbursement if possible, if not me, then Frapp.

And since this is my first post, I guess I'll introduce myself. My IGN is DMinecraftKiller, I have played mcpvp.com in the past but it has been a while, I am a pacifist in game unless you specifically want me to "1v1" you, I don't raid other players, and I've been grinding like hell for the past week to try and get the free Elite rank (Kinda hard to beat Trcgs realistically in 5 days though). Hopefully the potential bug I mentioned above can get fixed soon, and thank you for taking the time to read this.