If it was a Gmail account, it is now under the Junk Mailbox folder.
If you have any of the basic four folders (Drafts, Sent, Junk, Trash) separate in your IMAP server mailboxes, you can set them to be incorporated into Mail's unified mailboxes. Mail had previously captured the ones it was aware of, but left the others un-unified. All of Gmail's folders are now integrated.
To use an IMAP mailbox for a specific purpose, select it, then choose Use this Mailbox For from the Mailbox menu and set if for the appropriate function.
it's actually multiple accounts - work, home, coaching, etc...I've established different e-mail accounts to kind of "auto-sort" stuff... It's just odd that the separate "spam" folders just disappeared - great, if Mavericks Mail has consolidated everything into one...one less step! Thank You -- if anyone else has seen this with multiple "accounts", please let me know -- thanks!