According to the Syrian Arab News Agency, President Assad's "General Command responded to [an Israeli air attack] and shot down an Israeli warplane to the southwest of Quneitra." The same announcement also claimed to have shot down "an Israeli drone to the west of Sa’sa’ town in the southwestern countryside of Damascus." According to the report, this happened yesterday.
In fact, in response to a "spillover" rocket that landed in the Golan Heights on Monday evening, Israel did carry out a strike that same night. According to The Times of Israel, Jerusalem ordered hits that "struck Syrian army artillery targets on the plateau" portion of Golan controlled by Syria.
But according to Israel's military, the IDF, none of its jets were shot down. In a statement responding to the alleged downing, acknowledged that surface-to-air missiles at its aircraft but missed. "All Israeli jets returned to base," it said.
The Jerusalem Post reports that Israel's regards "spillover" rockets that land in the Israeli Golan as no different from "intentional fire."
According to Eli Malka, head of Israel's Golan Regional Council, "It is the responsibility of the Minister of Defense and the IDF to convey a clear message to all parties on the other side of the border that all shots fired in the Golan will be treated as firing on Israel and the IDF will respond by destructing the source of the fire."
Notably, the "spillover" rocked landed in Israel after a ceasefire declared by the US, Russia and Syria, began on Monday evening.