Yes, I do have a lock box. What I really like to do is meet the guests as it serves a few purposes - one of which is I get to see who is in my flat which is reassuring for me. I've never had to use the lock box so far, but it is my 'fall back'. But I always assumed, in that case, at least the guest would have contacted me. There are a few lock boxes where my flat is located as this area attracts a lot of holiday lets and there have been rumours of them being tampered with so I have always just wanted to use it as last resort and always try to arrange a physical hand over of keys.
This is just something new to me - a guest who hasn't responded and I wondered if other people experienced this, was it common. The longer I do this the bigger range of scenarios I will face, I just find this particular scenario a bit un nerving as it seems it could so easily be avoided with just a message from them. I have their mobile as well, and will do as the other post suggested - contact Air B&B first to see if they get a responce. Thanks for replying. I am, for the first time, faced with using that facility I have on my listing of 'self check in' and feeling nervous about taking the plunge.