Just wondered if anyone knows if a spam bot will be able to submit a form if there is no submit button on the page. Just trying to do some very basic spam prevention without using CAPTCHA. The thought is to use jQuery to render the submit button if the user interacts with the form in some way. Any thoughts would be appreciated.
A bot most definitely will be able to find your post button, if only infrequently.
A very popular method sort of like what you are trying is to create a honeypot form element. The editable honeypot fields on the form are invisible to people (you can use jQuery/CSS to hide these form elements). They are validated when the form data is posted and if they contain any input then the submitter must be a bot of some sort.
Using obscured field names, and validation can also stop these bots. If the email field must have an @ sign, and the bot can't tell which field is email and which isn't, the chances it will make a successful post have been greatly reduced.