"Sad irony" refers to a situation where something happens that is both unfortunate and unexpected, causing a feeling of sadness or disappointment because it seems contradictory or unexpected. Full definition
There has been a somewhat sad irony in the smartphone market over the past few years. (bgr.com)
With sad irony his legacy itself is threatened with erasure by a house fire devastating a portion of his collection, and his withdrawal from the public sphere and subsequent neglect as a figure. (wdw.nl)
The present sad irony is this: while fathers in intact families are doing (and, it seems, enjoying) more and more hands - on care of their children, there are fewer and fewer intact families. (religion-online.org)