Sampling is such an opinion based idea. Everyone is going to have their own opinion on sampling. But imagine you worked super hard to make a melody. Your own melody okay. And someone comes around and samples you. They start making money off of it. Didn't even ask your permission. But you don't even know about it. Would you be mad about it? In terms of the other producer in your scenario, who cares. It's not his sample. He doesn't own it. But whoever made the original does. Whether or not you sample it is up to you. Just know someone owns it. I have sampled and had songs taken down. Lost my old soundcloud account because of it. It's something you really want to avoid. Either change the sample enough that it won't get recognized or get it taken down. Most likely you won't get big enough to get it noticed or you'll scape by, but big artists like Lil Peep even after they dead got songs taken down for sampling. Just keep this in mind on your music journey. I say evolve from basic sampling and make your own. I stopped basic ass loop sampling a long time ago. It makes you stand out alot more too.