In certain cases, PointCache bake files can be lost. This results in reports like T70696 and could also be the cause of T56083.

PointCache bake files are saved to blendcache_{blendfilename}/{prefix}_{framenumber}_{stackindex}.bphys. In this case {prefix} is either the cache name or the hex-encoded name of the object the cache is attached to. {stackindex} is the index of the cache. This is generally 00, but is a higher number when there are multiple caches on the same simulation.

For example, an anonymous cache for a particle system on an object Cube will have prefix 43756265.

Since {stackindex} is based on the cache index of its user (f.e. the particle system), it can still be 00 for multiple caches. This happens when an object has multiple particle systems, each with their own cache. Each cache will have stack index 0, creating a conflict where manipulating one cache can delete or overwrite the files of another cache.

The particle system is marked End of Life, but the loss of files can still be frustrating to users. However, changing this implicit mapping for anonymous caches could easily break compatibility with existing files.

I feel that the minimum we should do is warn about this in the manual. And that's what this diff is doing. Maybe we could also add a warning to the UI when multiple anonymous caches are used on the same object?