On the day of the capitulation of the German armed forces, 8 May 1945, Filbert took leave of his colleagues from the Criminal Police in Flensburg and ‘hiked’, as he put it, to the state of Thuringia in central Germany. His aim was to learn how his family was, for they had been staying with Filbert's parents-in-law at the potash works in Volkenroda. Filbert thus remained loyal to Hitler's regime until well after the latter's suicide on 30 April and, in so doing, avoided the fate of many Germans who were in favour of surrendering without a struggle in order to prevent unnecessary destruction or loss of life, or simply so as to make a good impression on the new power holders, and were therefore murdered in the final weeks of the war by those still loyal to the regime. After he had verified that his wife and sons were still alive, Filbert went to the town of Bad Gandersheim in what is now the neighbouring federal state of Lower Saxony. There, under the assumed name of ‘Alfred Selbert’, he registered with the local authorities in the neighbourhood of Heckenbeck on 2 June 1945. His place of abode was listed as the Hilprechtshausen manor (Gut Hilprechtshausen), his profession as ‘agricultural worker’ and his marital status as ‘single’. Filbert selected the name ‘Selbert’ because he had operated under this name during his time with the SD and still retained the corresponding identity papers. Apparently, Filbert always possessed several ID cards. Filbert would remain in Bad Gandersheim for the next six years. During the immediate post-war months, both the US Army and the British Military Mission in Denmark, successor to the Supreme Headquarters, Allied Expeditionary Force (SHAEF) Mission (Denmark), were evidently interested in locating Filbert. The description of Filbert in the relevant US Army file ran as follows: ‘Born 8 Sep 1905 in GIESSEN [sic]; height 5'11” (1.80 m); thin build; small chest; dark brown hair; grey-blue eyes; long thin face, pale complexion, large pointed nose, very visible duel scars on chin; wears SS uniform and badly fitting civilian clothes.’

As of 25 June 1945, Filbert's wife, Käthe, registered with the local authorities in Bad Gandersheim along with her two sons at 8 Burgstraße (‘c/o Timmermann’). According to her local registration card, Käthe Filbert was ‘married’. From 1946, Käthe's parents were also registered at this address.