What to do when 3rd party BSD/MIT software doesn't include a copyright notice or license text?

[Alistair Davidson]

Hi there,

We have a software product that includes several small third-party  
Ruby plugins ("gems") which are all listed as BSD or MIT licenses. We  
don't modify them, and they're Ruby scripts so they're not pre- 
compiled, but interpreted - hence the source is always present as-is.
If we redistribute them as part of the product, we always include all  
copyright notices and license texts as required under the terms of the  
license. So far so good.

My problem is that for our next version, we're planning to include a  
couple of plugins which, although they're listed on their project page  
as BSD or MIT licensed, they don't actually include any copyright  
notice or license text in the original distribution, or anywhere else  
that I can find. So the question is, what's the accepted practise in  
these case? What do we need to do in order to comply with a license  
that requires we reproduce something that doesn't seem to be present  
in the original library?

Thanks,

Al