Leaver Buster did exactly what it it's supposed to, you just had (likely) a connection hiccup that prevented you from loading in.
It sounds like you might have some occasional and slight interruptions in your connection, so please head over to the Connection Troubleshooting Log Reader. There, you can submit the Network logs from your match(es) and the log reader will show if you were having ping spikes and packet loss.
It will then will direct you to solutions. Please work through the solutions it suggests, and if you need assistance or they do not work come back here and we'll try to help.
You can also narrow down the source of latency or packet loss by downloading the WinMTR Network Diagnostic Tool, then use that to run a traceroute to the following IP (allow this to run for 5-15 minutes);
104.160.131.1
https://i.gyazo.com/a4bdea8b79ca54760e1a6c81f990c133.gif