Oh yeah, absolutely! The thing you have to keep in mind--for manuscript and early print, in fact--is that individual broadsides and pamphlets weren't that likely to survive on their own. So where can we look for them?

Steven Justice, Writing and Rebellion, points out that several English chronicles seem to preserve the text of letters and broadsheets related to the 1381 Peasants' Revolt, even if the original pamphlets themselves are lost to the past.

Many medieval manuscripts aren't actually full books. Instead, they are miscellany--collections of multiple texts, usually in excerpts. These can come about in two basic ways, with both variations frequently combined in the same codex. First, different quires (groups of sheets) would be combined in the same volume. This is actually how a lot of our early printed pamphlets survive, too. Second, individual writers or scribes would copy bits and pieces of various texts into their own prayer book or commonplace book. It's pretty clear, for example, that one particular chapter of Henry Suso's Little Book of Wisdom enjoyed circulation independent of the (very very popular) full text. It's not that we have pamphlet-style copies of that chapter--instead, we see it alongside different sets of texts in many many individual prayerbooks and miscellanies.

The late 14th century poem Christus und die minnende Seele (Christ and the loving soul) is a lengthy text on its own, but it also circulated independently of that massive and rather disturbing chunk of text in broadside form, with a set of illustrations.

Letters are a fascinating case. While surviving medieval letters are typically gathered into "letter collections" which travel as a book or part of a book, many individual letters were used to send along a sermon or a prayer to the initial recipient or recipients (another fun phenomenon of medieval letters: their text was often re-used to send a letter to another reader. BCC before carbon copies, indeed). We don't have copies of Hildegard of Bingen's public sermons on their own, for example, but we have them sent as or with letters to particular clergy, copied into her book of letters. (We know they are sermons from the letters to her that she is responding to, also included in the collection).