You said it might come form the Ukrainian side. They downed their own missile?
It might/may come from the South-West, which is under Ukrainian control.
But the AD defense, be it Ukrainian or Russian, does not starts/stops at the frontline.
Russian forces may have very well detected the launch and intercepted it on its way. If it did come from the south-west, the targets could have been Izyum, Rubizhnye (or anywhere in between). These are two of the main hot zones in the area and approximate trajectory.
But the Ukrainian forces could have very well shot it down as well after mistaking it for something launched by either Russia or the DPR.
Not sure what are Ukraine radar and EWS capabilities in the region at the moment, but one could assume radar and EW systems would have been among the first targets since the war began.
Knowing the 9M79 has a reach of 163 to 185km (let's say max 200km), it could have been fired from anywhere within that circle (with kramatorsk at the center):
That being said, only serials numbers and/or markings could tell us who it belonged to.
Ukraine marks their objects with "вир", abbreviation of "вироб" ("изделие" in Russian), followed by the serial number.