In 1878, 114 Old Master engravings, which Colvin had purchased for the museum from London art dealer A. W. Thibaudeau, were stolen by a hansom cab driver. Although the driver was tracked down and charged, the engravings were never recovered and Colvin was required to cover their cost. Colvin paid the £1,537 10s to Thibaudeau from his own salary in instalments for many years, having initially to borrow £400 from Robert Louis Stevenson; a debt which he was still repaying to his friend in 1884.