When I was going to the island I think kapp'n stole my fishing rod and..

Maybe I'm not understanding you correctly, but it seems like you are mistaken. It sounds like you are concerned that your items are not with you on the island. If that's right, then don't worry. You cannot bring anything to the island, other than what you are wearing. Once you return to your town, you will get everything back.

If I'm wrong, and you are missing your items even after returning, then it appears to be a glitch. I haven't heard of anyone experiencing it before. If all you lost are a shovel and fishing rod, count yourself lucky. Those items are cheap and relatively easy to reacquire. To prevent this in the future, I recommend storing all items yourself before visiting the island.

Kapp'n doesn't actually steal your stuff, he only jokes about it. This happened to me as well, only after going to the Able Sisters, so I think it is a glitch.

True

He stolen silver rod, he DOES steal

Everyone, Kapp'n never steals items, he only jokes about it. If your items are gone, it must be a glitch or you've forgotten that you put the missing item somewhere else before you went to the island. I haven't heard much about this glitch so if it happens again, drop all your items on the beach before going to the island.

Kapp'n does steal stuff but only valubale stuff e.g. He stole my new year hat.

So this just happened to me, he returned my net and pole but not my shovel (all regular as I've only been playing a few days). I have a theory on this, as this is the first time it has happened it the many times I've gone to the island for money making-he gets angry when you press b to skip his songs, so maybe thats when he takes them? Anyone else who has lost stuff been skipping his singing?

I stayed on the island over night, so when I returned to my town, the day rolled over to the next one and it saved, teleporting me back to my house, and my net disappeared. I think he does steal stuff. First time it's happened to me though. I will be more cautious from now on.

Kapp'n just took your items and he did that to me but don't worry when you return to your town your tools will be back k .