sort works on lines, not words.
For the example you've shown us, you're sorting a single line of text. For example:
$ echo 2.text 11.text 3.text | sort -n
2.text 11.text 3.text
But that's inconsistent with the output you've shown us, so I can't be sure just what you're doing, or what you're trying to do.
Are you looking for something like this?
$ echo 2.text 11.text 3.text | fmt -1
2.text
11.text
3.text
$ echo 2.text 11.text 3.text | fmt -1 | sort -n
2.text
3.text
11.text
And do you need to re-assemble the lines into a single line? Piping the output through fmt -999 will do that, but that's a bit ugly (GNU coreutils fmt limits the width to 2500).
-r?