I have one that is almost impossible to see the number. As you say could be cavity 2??
There are some molds Arno where it is hard to find the number and I have not found it in the weightliftersmurf-mold. Only on the weight-bar.
Have you found it on that smurf??
The problem is when it is a glued 2-piece mold then it can be on places where Schleich put glue and then it is impossible to find. So it could be on the head under the bar or in the hands under the bar??