Is Mayor Felix C Atus (below right) all that he seems? Photo: AnonyMouse
Both the new mouse-sized establishment that is the final destination in the treasure hunt (so far unseen by Instagrammers), and the reward issue of Lindenkronan, the city newspaper the collective has invented for the mystery, are nothing short of brilliant.
It's a fun detective mystery, featuring recorded mouse messages, four locations (three of whom feature new mouse establishments), two maps, and two newspaper front pages.
The last place you visit might be AnonyMouse's best yet, up there with II Topolino and Noix de Vie, the collective's first mouse restaurant and delicatessen, or the Sacre Blues jazz club that appeared on the streets of Bayonne, France.
It's also the first mouse establishment in Malmö not to be hidden in the cellar ventilation holes of a building, instead making ingenious use of a common piece of street furniture.
But as well as being a brilliant treasure hunt, Mustisk is also a piece of left-leaning satire.
First you have to find the offices of private detective Olivia Flaversham (a named shared by the heroine of Disney's The Great Mouse Detecive) and then send an email to an address on the poster volunteering your services.
You are then sent an issue of the Lindenkronan newspaper.
The newspaper introduces city mayor Felix C Atus, whose suspicious appearance should alert observant participants to the fact that he may not be a true “mouse of the people”.
Atus, the newspaper reports, had earlier decided to spend “a large proportion of this year's budget on a proper spectacle”, where all the “upper crust gnawers of Malmö” could enjoy a slap-up festive meal.
The city has also purchased a “record wheel of cheese”, which it has placed in an exhibition centre, hoping to bring tourists and other visitors to the city. The cheese, however, has been stolen from Malmö's cheese bank Fort Nux by a mysterious villain.
Another article warns of growing “homelessness and food shortages” in the city.
“Privatization is having its impact and many no longer have the resources to have their own little hole any longer,” laments Klas Klättermus, chief executive of the Tass i Tass (Paw in Paw) homeless shelter (which appeared in Malmö last December).
All of this amounts to a fairly unsubtle jab at Malmö's Social Democrat-led government, which in the last decade, has invested heavily in Malmö Live, a glitzy concert hall and conference centre, at the same time as social services face cut backs and class sizes in the city's schools grow inexorably.
The gentle satire underpinning the whole treasure hunt is reminiscent of Bamse, the Swedish cartoon bear who is in a constant battle with the arch-capitalist Krösus Sork and who is rumoured by some to be an actual communist, with one 1983 issue lauding Chairman Mao.
Judging by the fact that AnonyMouse's Lindenkronen newspaper, if you look carefully, was founded by none other than Krösus S. Sork, this similarity appears not to be accidental.
At Fort Nux there's a phone number and if you ring it, a recorded message left by Flaversham directs you to a third location.
At the third location, you find a map with a fairly obvious lead to the location of the establishment run by the person or persons behind the robbery.
Who would want to steal so much cheese? Is it an insurance job? Is Mayor Atus all that he seems? Could he himself be the thief? What is the meaning of the mysterious acorn symbol?
It's not too tricky to find out.
Although slightly over the head of a five-year-old and a seven-year-old (they enjoyed the models), you would only have to be a few years older to finish it in less than an hour.
And if you live in Malmö, you should really get off your phone and do it.