I have problems with grasshoppers sometimes, especially in late summer. They eat the flower spikes, but they are big, so you can see great big chomp marks taken out of the spikes. Your damage doesn't look quite like the damage I get from those huge grasshoppers, so maybe be looking for something smaller. Your climate is very different from mine, so I'm not sure what pests are common in your area, but maybe be on the lookout for slugs or snails. If you're not seeing any of the offending creatures during the day, maybe wait until night and go out there with a flashlight, as some pests are nocturnal, and maybe you can catch them in the act then. But regarding the frog, the frog is your friend. He will eat a lot of the things which can cause trouble for your orchids. Next time you see him, you might tell him thank you