Nick is correct...
In the Delay models, try using the "Reverse". Set the TIME to a "note value" for Tap Tempo control of the repeat rate. Setting the FDBCK parameter to 0% will give you a single-pass reverse repeat of what you play. MODSP to 0% and DEPTH to 0% (unless you want some modulation to your sound) and set the MIX to 100%.
This should approximate your Boomerang's reverse sound (I used to have one; I remember that effect).