Why might a place ‘disappear’ between one census and another?

The most likely explanation for this is that the place concerned has been affected by a boundary change. Changes to parish, county and burgh boundaries were made throughout the 19th and 20th centuries, but the principal changes were made by Boundary Commissioners set up after the 1889 Local Government (Scotland) Act. Over 3000 settlements in Scotland were affected by either parish or county boundary changes, or both, in the period 1890-91. In addition, many suburban settlements were annexed by burghs between the mid-19th and mid-20th centuries. If a place appears to have ‘disappeared’ between censuses (or, indeed, between years in other records, such as valuation rolls) you should check Francis H Groome, Ordnance Gazetteer for Scotland (1896 or later editions), which contains information derived from the Boundary Commissioners reports. If the place itself is not mentioned because it is quite small, check under the parish concerned to see if it was affected by a boundary change. Alternatively check the General Register Office for Scotland’s Index of Scottish Placenames from the 1971 Census (HMSO, 1975) or Index of Scottish Placenames from the 1981 Census (HMSO, 1985) – both of which give the civil parish and county for settlements with a population of 100 or more.