Should getting no response in this timespan be understood as a no? What should I do in this situation? I am starting my Ph.D. and am interested in a specific field of research which seems quite promising for the next years. Now, my masters supervisor does not work in this field, nor anyone in the department, and it seems in the country. 

Nonetheless, he is interested and suggested me to find an expert in the field from another country to collaborate and said he would sign a recommendation letter1. In the better scenario this would be a formal co-supervision, but not a requirement.

So, I sent an email to such an expert (in fact it seems one of the researches who started the field) with my masters thesis attached as well as the recommendation letter. After a week unfortunately I didn't get any response.

I asked my masters supervisor and he suggested me to reply the email resending it, because he said that usually there is an answer. He also told me to add one line asking if someone else could be suggested.

I've sent the message last week and no answer as well up to now.

To be honest I'm confused. I mean, the thesis has been quite complimented by a very famous researcher in my country who integrated the examination board. The recommendation letter speaks quite well about my work. Finally my university seems to be respected internationally. With all this, I thought at least a no as answer I would get.

Perhaps the only point is that I have not worked in that field in my masters, but that was because no one in the country knew it.

Now, is this lack of response, in the timespan I told about, effectively a no, totally dismissing the possibility, and so should I already disconsider it? Or a no would be really be said explicitly? Should I wait more before looking for some other possibility?

Edit: In trying to make the question more concise and to the point (whether or not one could expect an answer in the timespan of more or less 10 days) I left out a detail. The email was focused on asking for a collaboration. Of course, formal co-supervision would be better, but it is not required, and we briefly mentioned it. So the email was entirely focused on collaboration. The scholarship pays for just a collaboration also, where the PhD student spends one year working on the group of another researcher. 



1. I don't know how things are done in other places, but here it is possible to establish a collaboration with a researcher from anywhere, including other country, and have it all paid by the scholarship if you need to stay a certain time working there with him. This may or may not be a formal co-supervision, so that the researcher has the option to not sign if he cannot.
Your time scale seems too short for me. Patience might be a virtue here. But sending the thesis and the request at the same time is probably a pretty heavy load to drop on a person. 

Ask your advisor to follow up with a request and a recommendation. It might be more successful coming from them than from you. 

But in general, making a request and offering to show related work in the initial request might be more successful than just sending it all at once. Some people get a lot of these requests and have learned to ignore them.