Chapter numbering breaks by skipping a title

I'm translating a book and the original has the following headers:

1

1.1

1.1.1

1.1.2

1.2

1.3

2

3

3.1.1

My level 3 numbering uses ^1.^2.^#

What happens is that, since ther's no 3.1, the numbering starts from the last level 2 title used (1.3), this way:

[omissis]

3

3.4.1

Is there anything I can do save a white-on-white 3.1 (that ruins my automatic summary) or faking it with a dangerous 3.1.^# title style?