Francesco Visalli, a fellow Mondrian enthusiast, has drawn to my attention an article from the RKD dated 10th July 2017 entitled, RKD solves mystery of an unknown painting by Mondrian. The article states,

A recently discovered photograph of the 1925 Mondrian – Man Ray exhibition at the Dresden gallery Kunstausstellung Kühl & Kühn [right] has enabled Wietse Coppes, curator at the RKD – Netherlands Institute of Art History, to identify a painting by Piet Mondrian that was previously known only from an inventory. The photograph was found in the archive of Mondrian expert Joop M. Joosten (*1926) which recently came to the RKD.
The painting is described in the inventory as Komposition XIV, 1922, measuring 62 x 62 cm, but without an image. It was included in the 1998 catalogue raisonné of Mondrian’s work solely on the basis of this information. The exhibition photograph shows us the actual painting for the first time; it can be seen to the left of the doorway.
This also solves a second problem which concerns another unidentified painting in the same catalogue raisonné, in this case a work which was, interestingly, only known through a reproduction in Mondrian’s estate [above]. Thanks to the photograph of the gallery Kunstausstellung Kühl & Kühn, it was possible to match the work mentioned in the inventory to the reproduction. Regrettably Komposition XIV was lost during the Second World War. For this reason and because we only have black and white photographs, the colour scheme of the painting can no longer be established.

This gives a size and a new title and date for the work, described in the Catalogue as 1926/27.

Sources: RKD