Just to add to my previous post - I didn't find teaching the recall command difficult with my hound at all, she picked it up very quickly. It was getting the recall reliable, and working out how to disrupt her when she was on a scent so she was actually aware that I was calling her.

When she is aware I am calling her she has a great, very speedy recall, excellent focus etc - but if she has her nose to the ground on a serious scent then the instinct has taken over and she's not even aware that I am near her, or calling her, all her brain is able to focus on is following the scent.

I agree with DT's suggestion of putting the dog on a tracking lead, it is by far the safer option for now.