Preference: I think 3 is a non-starter; anything could be a watchword, it doesn't need to be the statue.
We lack the information about the kobolds' attitude to the statue to decide between other options. Is it treasure? is it a trophy of a victory? Is it something they would want made as an offering (and if so is vicarious offering appropriate/acceptable to their worldview)? We don't kw, and any calling attention to it means that chances of stealing it go down.
If it is stolen, we can have an illusory substitute for a minute.
My guess is 2. is more likely to work than 1., but knowing the kobolds' attitude to the object would help.
