Thanks to all who have given advice on how to retrieve items dropped behind the Murphy bed.
It is very easy to leave something on the bed and then put the bed up. After having this experience I have tried to check the bed more carefully before I put it up but now that I know there is an access panel in the front pass through compartment I am not as worried if I make a mistake and drop something down behind the bed.
I do wonder why Winnebago did not put an access panel or door to the space under the bed inside the coach. There is a fair bit of room under there which basically is wasted space. I guess as suggested if you want to hide something in your coach you could open up the access panel and put the item(s) in there. The space is certainly not readily accessible and if you did not know where to look you would miss it.
Thanks again everyone and happy camping.