Master thesis: should I say that some results are a novelty in the field? I am nearly at the end of my master thesis and, according to my research, the last part of it deals with something that has not been treated before in any paper/book I have found. 

To make things more clear: in my thesis I am applying a method well known in literature, which has been applied many times on simple structural elements built on purpose to validate the method. In my thesis I have started applying the method on simple structures too, to be sure I have implemented it correctly. Then, in the last part, I apply it on a real-world structure using real measurements (not numerical generated ones).

The problem is that I am not sure if I should underline this fact as a novelty in the method application. According to my literature research, this approach has not been tried yet, but I can speak only 2 languages, therefore I looked for books/papers written in those 2 languages only. 

What if this thing has been already done by someone else on a paper written in another language? Then my results will not be a novelty anymore, so I should not mention it in my thesis and this will also affect the 'goodness' of my work too (because my thesis will not actually add any useful information to the already existing literature).

How can I deal with this situation?
This is a common situation, since it really isn't possible to be absolutely certain that nobody has done this work before. What I find people usually do is:


Do the best literature search you can. As for references in other languages, in many fields it's  common that papers written in, say, French, will have an abstract in English, so you'd have a chance of finding them even if you can't read French. But if you find a French paper whose abstract suggests that it may contain similar results to yours, then it is your duty to find a way to read it (look for a translation, ask a colleague to translate, learn some French yourself if necessary) and make sure.
Once you are satisfied you have done a diligent search, write something like "this result appears to be new" or "as far as we know, this result has not been obtained previously". 
If it later turns out that your result was already known, be prepared to acknowledge that the other author had priority, and to be able to show that although you did a reasonably diligent search, you did not find the prior paper, and that your result was truly obtained independently (not plagiarized).