There has been the odd sighting, but, by the time the men with the tranquillising darts have shown up, Yvonne has melted back into the depths of the pine forest.
Yet if humans have been unable to make contact with her, she, apparently, has got in touch with them. An Austrian animal psychic claims to have telepathically reached Yvonne, who has reassured her public that she is OK, but still too afraid to give herself up.
All this has added to her growing legend.
German media have embraced her as a welcome respite from the travails of the eurozone, Facebook groups dedicated to her have tens of thousands of followers, and a song by a band called Gnadenkapelle is played incessantly by radio stations.
"Why don't you leave Yvonne alone, she's only a runaway cow ... You wild cow, don't let them take your freedom," runs the lyric, the snappiness of which may have lost something in translation.
A looming deadline, however, hangs over her. In the early days of her escape, Yvonne nearly collided with a police car, and the authorities in Muehldorf declared her a public danger who should be shot on sight.
Animals activists rallied, the president of the Universal Society of Hinduism issued a condemnatory statement, and the order was rescinded - until Friday.
An animal sanctuary with branches near Salzburg, Austria and Munich, Germany has bought Yvonne, and cancelled her date with the slaughterhouse, and promised it will ensure that she sees out her days in pastured contentment.
As a result, gentler methods have been deployed to try to lure her back into captivity. Her sister Waltraud was tethered in a likely area, in the hope that the prospect of a family reunion might act as a lure.
The bellows of her son Friesi were recorded and have been played in the woods, alas without success.
And there has even been an attempt to play on what you might call her more animal instincts. A bull called Ernst was brought to the relevant areas, but his magnetism failed to work. This may, or may not, be connected to the fact that Ernst has been castrated.
There were fleeting glimpses on Thursday, and the only known photographs of the absentee cow show Yvonne to be worryingly thin. There are also reports that she has been seen with a herd of deer.
But last night, as darkness fell, the 680kg Yvonne was still very much at large.
One of the songs spawned by the story of Yvonne the runaway cow
- INDEPENDENT