I have a problem with a thumbnail video post. Whatever virtual template I did not use in a thumbnail all I see is the text of my link on YouTube

please help, how to look a virtual template in this case

how are you getting the thumbnail video - a plugin?
look in the virtual sub template postformat.php and you may need to change the bfa_excerpt() to something else.

Note: if you change it to 'the_content()' thise is an issue. Look thru the recent posts for a potential fix.