A fellow gardener potted on some brassica plants which he had brought on in his greenhouse. The plants had grown to 5/6 inches in height and were in 3 inch modules. A few days ago he found that some of the plant stems had been cut/severed, but there was no sign of the missing stems and leaves. Later on, he found the stems and leaves intact, not having been nibbled, in a gap under a tray adjacent to where the plants were. They had obviously been carried there by the culprit, but left untouched! He has mousetraps set, but I do not think that mice tamper with brassicas, and would not in any event transport them to a "store". There is no sign of slug damage.

Baffled. Any ideas?