In order to use a bow on a stringed instrument, in any conventional way, it's necessary to be able to get the bow on a single string at a time, or to various pairs/groups of strings, without hitting the other strings. The flat layout of the strings on an autoharp makes this pretty much impossible. If you bowed across all of the strings, you'd only move the ones at the edges, and the bowhair would be nearly out of contact with the strings in the middle.

A number of instruments all "look a lot alike" but actually are quite difference. For reference:

bowed psaltery

autoharp

simple Zither

fancy Zither

Ukelin

Ukelin music??????

The bowed psaltery has a "bridge" at the base end of the strings, but the upper ends connect directly to the tuning pegs. The difference in string lengths allows a "gap" in which the bow can contact any single string. Alternate strings are arranged along the two sides to make the gaps just large enough to fit a bow between the pegs to pick which string to play.

While it might appear that there are gaps between the pegs, at least at one end of some of the pegs on an autoharp, the active string length is "cut off" by a "bridge" at one end and a "nut" at the other, so there's no place to get the bow onto the "working part" any particular string to bow it.

The simple Zither has the same problem as the autoharp, with the working string lengths determined by bridge and nut bars that would prevent getting a bow onto the strings.

The most promising adaptation of a zither might be done with the "fancy Zither" since the "guitar strings" along the edge could be run over a "ramped/convex curved bridge" to bring those few strings up to where a bow could get to them, but it would probably be appropriate to retune those strings like a fiddle, rather than what's most likely used for a "guitar like" fretboard. A conversion presents several interesting puzzles to be solved.

It's quite likely that what was seen being played with a bow was a bowed psaltery. And it might be noted that for purposes of experimentation one of the simple psalteries would likely be much cheaper than the costs of modifying another kind of instrument. Those who play the psaltery generally prefer bows much smaller than the usual fiddle bow, since the bow has to jump from string to string a lot, but even a little investigation should find decent enough information to decide whether to dive into one.

John