They do exist.

In the last couple of years, I have really slowed down as far as collecting for several reasons.  First, I have a lot of bonnets and have gotten rather picky.  I really don't need several of the exact same thing.  Second, the bonnets I find are just too expensive and I am not finding the deals I once did.  That changed recently.  I found two incorrectly marked relatively inexpensive bonnets.  

The first bonnet was labelled as a sunbonnet and was pointed out to me by my friend Anna Worden Bauersmith.  Anna and I will point bonnets out to each other that we feel that one of us "needs." The pictures were not great, but the shape was right for mid 1840s bonnet.  The seller described the bonnet as in poor condition, but for $20 plus shipping I was willing to risk it just to study the shape. 
I received the bonnet and opened it to find it in excellent condition for a bonnet that is almost 180 years old. It is dented, but the silk faille fabric is in very nice condition.  The brim, made of both buckram and pasteboard, makes it a transitional piece from the early to mid 19th century.  

The second bonnet was also pointed out to me by Anna.  It was labeled 1880s. 
A lot of bonnets are labeled 1860s when they are 1880s, but not the other way around.  This bonnet has all the characteristics of a mid 1860s Empire bonnet.  It has points which are not present on 1880s bonnets.  It has a little flared piece under the bavolet characteristic of mid 1860's bonnets.  Another super cool thing about this bonnet is the trim.  First of all, I am thrilled that it still has trimming, but even more what the trimmings tell me about this bonnet.   Almost all black bonnets are labeled mourning bonnets, they are not.  This one is.  The presence of crape and flat rather than shiny ribbons indicate that this bonnet is indeed a mid 1860s mourning bonnet.