gnome-contacts: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/gnome-contacts - from package: gnome-contacts

You may install the required package with command apt-get install {package}

Error in other languages:
gnome-contacts: bevel nie gevind nie
gnome-contacts: comandă negăsită
gnome-contacts: comando não encontrado
gnome-contacts: commande introuvable
gnome-contacts: command not found
gnome-contacts: käsku ei ole
gnome-contacts: không tìm thấy lệnh
gnome-contacts: komanda nerasta
gnome-contacts: Kommando nicht gefunden.
gnome-contacts: kommandot finns inte
gnome-contacts: komut yok
gnome-contacts: nie znaleziono polecenia
gnome-contacts: níor aimsíodh an t-ordú
gnome-contacts: no se encontró la orden
gnome-contacts: no s'ha trobat l'ordre
gnome-contacts: opdracht niet gevonden
gnome-contacts: parancs nem található
gnome-contacts: perintah tidak ditemukan
gnome-contacts: príkaz nenájdený
gnome-contacts: příkaz nenalezen
gnome-contacts: команда не найдена
gnome-contacts: командата не е открита
gnome-contacts: 命令找不到
gnome-contacts: コマンドが見つかりません