Do we ever, in a research paper, mention methods we tried but did not get a satisfactory result?
I cannot see any reason not to mention what could be labelled "negative results". If you have tried a method and it failed there can be two reasons, either the choice of method was bad (which is likely a trivial unpublishable result) or the method is in some way not appropriate due to reasons not before understood. In the latter case, there are clear advantages to convey this result to others. This may spawn new research or simply help others avoid using the method. Hopefully you will be able to provide deeper insights into why things did not work out as you first thought. In essence, anything that progresses our understanding is worth bringing forth in a publication.