These areas were imaged hundreds of times by VMC, but the hot spots only appeared very briefly. Crucially, two of the hot spots appeared in more than one orbit right after the other -- so it wasn't just one spurious detection. From the supplemental information to the paper, here's what we know about the hot spots:

Spot "A" was observed on orbits 793 and 795 (June 21 and 24, 2008). If the spot was actually a very small area (less than 1 square kilometer), it might have been 900-1000K on orbit 793 and 900-1100K on orbit 795, then was not observed after.

Spot "B" was observed one Earth year later, on orbits 1147 and 1148 (June 10 and 11, 2009). Depending on its size, it might have been 800 to 950K.

Spot "D" was observed on orbit 1148 (the same as spot B) It might be a larger area 800 to 900K.

These are not quite "liquid hot magma" temperatures, but they're very close. If VMC was seeing the cooling surface of a lava flow, those temperatures would be very reasonable.

In making the map, I noticed that the paper seems to have a nomenclature error: they talk about "Ganiki Chasma," but they're actually talking about Ganis Chasma; its name has been confused for nearby Ganiki Planitia. (Ganis Chasma was named for a western Lapp forest maiden, while Ganiki Planitia was named for a Siberian water spirit.)

Do enlarge the top image by clicking through it twice to enjoy the beautiful diversity of the Venusian landscape. This area has it all: small shield volcanoes and gigantic volcanic constructs; wide spreading lava flows; impact craters, some of them filled by lava; a particularly fresh impact crater (Sitwell) with a dark parabola; and that system of fissures. Here is one zoom in on the region containing Shalygin's Objects A and D. I feel like I can almost make out landslides running down the chasm walls here. Magellan image resolution is always just short of what I really want to see the features I'm interested in.