It sends it to the server to do the query since the web UI only has a small store of data. So, the display shouldn't get out of sync, but I could imagine that you type something, the grid is cleared while it sends query for the new data, and maybe something was happening on the server and the client maybe timed out.
Though, thinking about it, I used to have hangs many months ago where the UI just stopped working since the server had "queued 2mb data", which was caused by box (at the time) deciding to use very poor wifi instead of ethernet to access its remote disks/tuners. So, it's not inconceivable that there was a mini-problem, but it doesn't really account for you being to retype and get new results instantly.