I would suggest you forward their camp invitation e-mail back to them, with a forwarding note asking if this was intended for you and if so, did they mean to invite you to the position players camp, as you are not a pitcher.
Please choose your words carefully so as to present this as you being genuinely unclear as to whether the invitation might not have been intended for someone else -- a case of mistaken identity. The key is not to come across as irritated or impertinent. You want to sound interested, but basically asking to be invited to the correct camp.
Your hope would be to generate a more individualized reply from them, that might illuminate you more as to where you truly stand.
But again, you won't get that if your note sounds like, "Hey dummies, I'm not a pitcher!" Anything that gives a whiff of that attitude will risk doing permanent harm to your prospects.
I find that most teenagers are accustomed to approaching adults familiarly, and it comes as quite a surprise to them to discover that most coaches get prickly when this happens. It's understandable, because many of these players have been told over the years, e.g., to address their coaches by their first names. But however understandable it may be, it's wrong. The social convention is that minors are to address adults by their surnames (Mr. Smith or Coach Smith) unless and until the adult explicitly invites the young person to address them more familiarly. And this rule applies on an adult-by-adult basis, which means that just because lots of adults are OK with the player being familiar doesn't mean that the next one will be, or even that he should be. That decision is the adult's to make.
When I tell players this, they often say things like, "Well that's just stupid." Meaning, they intend to just keep on speaking to adults as if they (the players) were the adults' equals. My reply to that is to explain that, whether they like it or not, societal conventions have been developed over centuries by billions of others, and the rest of the world is not going to change to suit them. So if they want to have the system work for them, they'd best get used to the idea that they are in a subordinate position in this universe.
Treat this like you are applying for a job, and you therefore expect to address your future boss with total respect. If you are experienced doing this, great. If you are not, then until you get the hang of it, write your own e-mails but ask a parent to check them over before you click the "send" button. It's a fine line you're walking here, so you need to tread lightly so that you move up on their list, instead of ending up scratched off it.
