  We study the non-equilibrium version of the fluctuation-dissipation theorem
(FDT) within the glass phase of Bouchaud's trap model. We incorporate into the
model an arbitrary observable m and obtain its correlation and response
functions in closed form. A limiting non-equilibrium FDT plot (of correlator vs
response) is approached at long times for most choices of m, with
energy-temperature FDT a notable exception. In contrast to standard mean field
models, however, the shape of the plot depends nontrivially on the observable,
and its slope varies continuously even though there is a single scaling of
relaxation times with age. Non-equilibrium FDT plots can therefore not be used
to define a meaningful effective temperature T_eff in this model. Consequences
for the wider applicability of an FDT-derived T_eff are discussed.
