II am so sorry to hear that you are having a hard time getting Luna to stop eating pebbles and other things she shouldn't. . Puppies absolutely do like to get into things they shouldn't, as frustrating as this can be.
To keep Luna safe from the possible harmful effects of eating things she shouldn't, try to keep her in an area devoid of these items while you are out. If this isn't possible try the following tactics;
Increased exercise especially a long afternoon or evening walk
Chew toys
Puzzle toys
Interactive games like fetch and hide and go seek
Leaving the TV, a fan or a White House generating machine on
DAP- dog appeasing pheromone releasing diffusers
Thunder coats
http://m.drsfostersmith.com/product/prod_display.cfm?pcatid=24037Here are some further resources to help you, but also feel free to ask me any for their questions here on the forum.
https://www.petcoach.co/article/10-ways-to-stimulate-your-dog-s-brain/https://www.petcoach.co/article/7-ways-to-make-sure-your-dog-feels-safe-in-your-home/https://www.petcoach.co/article/10-signs-your-dog-is-stressed/One reason why puppies are known for their destructive tendencies is they are in need of more stimulation, or experience anxiety when separated from you. There currently are several toys on the market which will interact with Luna and release treats, that can be used while you are out. Luna could also possibly benefit from more exercise, as well as puppy socialisation classes.
I hope this was a helpful answer and more importantly that Luna feels better soon. I don't think she will be ill again, and you can try a bland diet of boiled chicken and steamed white rice to calm her gastrointestinal tract for a few days. Warmest regards and best of luck to you both