This is in a common location but hidden in a non typical way. It is NOT magnetic, completely out in the open, and you can look directly at it without realizing it. It looks as if it belongs there. This is a high muggle area but if you position yourself in front you should be able to extract and replace it most any time. Please be careful removing the log to prevent tearing.
When replacing the cache kindly insert it all the way so that it is deep inside, snug but removable.