You could cast a resin base into the hole....very on trend
If you were a golfer you would be proud with that hole in one.
Peter.
As you have found out [MENTION=1856]Frederick[/MENTION] when turning using a mortice that you can go through the bottom that is why it is very important to keep measuring Most of the time I use a tenon and then reverse chuck it and remove it.
A shame really as it looks like it was going to be a great bowl As Mark said either fill it with resin after cleaning the hole or use a piece of wood in a contrasting colour this makes it look like it was intentional