Can I say that all the keywords you say you searched (and are in the search terms) are all found in your Nelson Mandela article, and Lithuania is used in the comments to that article. Therefore one of your articles has all the required keywords.
The reason you are not showing up when YOU search is because you are (probably) doing a quick search through the first 10 pages of Google.com
Remember that search results can show up in Google Images, Google Blogs, Google Discussions and even (but hardly likely in this case) Google Video searches. It may be through these that they found you. For example, I too have had many strange search terms appear and yet they all match relevant articles on my site and when digging deep enough you can sometimes find why they found it, for example, a generic term like "Miley Cyrus" may not turn up your result in the first 10,000,000 results on Google.com, but might turn up in the top 50 images if you have a funny image with that search term.
You also have to remember that Google.com may throw up totally different search terms (and therefore ordering) than Google.co.uk, or in this case I suspect Google.co.lithuania (or whatever domain suffix they use out there). It might be that your article about Nelson Mandela could be placed 7th top search result for that group of search terms in Lithuania (well done, you are famous in Lithuania!) whereas only 7,999,999th in Google.com (still a way to go in the US of A!)
So bear in mind that the search keywords that appear are likely to be real users but coming from locations you never thought off. I for one had a strange search request that I swore was not normal for me to be showing up on a search results, and yet a mobile phone application that used Google Image Search (much like Facebook Messenger uses Bing Image search to send random images to friends) was throwing up the photo on my obscure article on page 1!
On a side note, have you signed up to Google Webmaster Tools and verified your domain with them? If you do that then you can track your search terms much more accurately and see where they are finding you and at what page on the search results your articles search terms are usually found. It might solve some of the mystery around some of the searches!